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package util;
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import generator.Problem;
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import java.util.*;
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public class ExpressionUtils {
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private static Random rand = new Random();
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private static final String[] OPS_PRIMARY = {"+", "-", "*", "/"};
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private static final String[] OPS_MIDDLE = {"+", "-", "*", "/"};
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//private static final String[] OPS_HIGH = {"+", "-", "*", "/", "^2", "sqrt"};
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public static String randomNumber() {
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return String.valueOf(rand.nextInt(100) + 1);
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}
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// --- 表达式求解和选项生成辅助方法 ---
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public static double solveExpression(String expr) {
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// 预处理表达式，确保格式正确
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String parsableExpr = expr
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.replaceAll("(\\d+|\\([^)]+\\))\\^2", "pow($1, 2)") // 处理平方
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.replaceAll("sqrt\\s+(\\d+)", "sqrt($1)") // 处理缺少括号的sqrt
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.replaceAll("\\s+", " "); // 标准化空格
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try {
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return new Object() {
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int pos = -1, ch;
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void nextChar() {
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ch = (++pos < parsableExpr.length()) ? parsableExpr.charAt(pos) : -1;
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}
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boolean eat(int charToEat) {
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while (ch == ' ') nextChar();
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if (ch == charToEat) {
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nextChar();
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return true;
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}
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return false;
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}
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double parse() {
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nextChar();
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double x = parseExpression();
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if (pos < parsableExpr.length()) throw new RuntimeException("Unexpected: " + (char) ch);
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return x;
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}
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double parseExpression() {
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double x = parseTerm();
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for (; ; ) {
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if (eat('+')) x += parseTerm(); // addition
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else if (eat('-')) x -= parseTerm(); // subtraction
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else return x;
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}
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}
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double parseTerm() {
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double x = parseFactor();
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for (; ; ) {
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if (eat('*')) x *= parseFactor(); // multiplication
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else if (eat('/')) { // division
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double divisor = parseFactor();
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if (divisor == 0) throw new ArithmeticException("Division by zero");
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x /= divisor;
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} else return x;
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}
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}
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double parseFactor() {
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if (eat('+')) return parseFactor(); // unary plus
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if (eat('-')) return -parseFactor(); // unary minus
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double x;
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int startPos = this.pos;
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if (eat('(')) { // parentheses
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x = parseExpression();
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eat(')');
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} else if ((ch >= '0' && ch <= '9') || ch == '.') { // numbers
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while ((ch >= '0' && ch <= '9') || ch == '.') nextChar();
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x = Double.parseDouble(parsableExpr.substring(startPos, this.pos));
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} else if (ch >= 'a' && ch <= 'z') { // functions
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while (ch >= 'a' && ch <= 'z') nextChar();
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String func = parsableExpr.substring(startPos, this.pos);
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x = parseFactor();
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switch (func) {
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case "sqrt":
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x = Math.sqrt(x);
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break;
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case "sin":
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x = Math.sin(Math.toRadians(x));
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break;
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case "cos":
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x = Math.cos(Math.toRadians(x));
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break;
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case "tan":
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x = Math.tan(Math.toRadians(x));
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break;
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case "pow":
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eat(',');
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double y = parseExpression();
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x = Math.pow(x, y);
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eat(')');
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break;
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default:
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throw new RuntimeException("Unknown function: " + func);
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}
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} else {
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throw new RuntimeException("Unexpected: " + (char) ch);
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}
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return x;
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}
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}.parse();
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} catch (Exception e) {
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System.err.println("Error parsing expression: '" + expr + "'. Parsable version: '" + parsableExpr + "'. Error: " + e.getMessage());
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return Double.NaN;
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}
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}
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private static String formatResult(double result) {
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if (Double.isNaN(result)) {
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return "Error";
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}
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if (Math.abs(result - Math.round(result)) < 0.0001) {
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return String.valueOf((int) Math.round(result));
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}
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return String.format("%.2f", result);
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}
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/**
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* MODIFICATION: 确保为整数答案生成整数干扰项
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*/
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private static String generateDistractor(double correctResult, List<String> existingOptions) {
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if (Double.isNaN(correctResult)) {
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return String.valueOf(rand.nextInt(100));
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}
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// 检查正确答案是否为整数
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boolean isIntegerResult = Math.abs(correctResult - Math.round(correctResult)) < 0.0001;
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double distractor;
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String distractorStr;
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do {
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if (isIntegerResult) {
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// 生成一个整数干扰项
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int offset = rand.nextInt(20) + 1; // 扩大随机范围以避免重复
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distractor = rand.nextBoolean() ? Math.round(correctResult) + offset : Math.round(correctResult) - offset;
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// 确保干扰项不为负数
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if (distractor < 0) {
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distractor = Math.round(correctResult) + offset;
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}
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} else {
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// 答案是小数，则生成小数干扰项
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distractor = correctResult +
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(rand.nextInt(10) + 1) * (rand.nextBoolean() ? 1 : -1) +
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(rand.nextDouble() * 0.9);
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}
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distractorStr = formatResult(distractor);
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} while (existingOptions.contains(distractorStr)); // 确保选项不重复
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return distractorStr;
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}
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public static List<String> generateOptions(double correctResult) {
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List<String> options = new ArrayList<>();
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options.add(formatResult(correctResult));
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for (int i = 0; i < 3; i++) {
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options.add(generateDistractor(correctResult, options));
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}
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Collections.shuffle(options);
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return options;
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}
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public static Problem createProblem(String expression) {
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double result = solveExpression(expression);
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// 如果解析失败，返回null，让调用者重新生成
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if (Double.isNaN(result)) {
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return null;
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}
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String correctAnswerOption = formatResult(result);
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List<String> options = generateOptions(result);
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return new Problem(expression, result, options, correctAnswerOption);
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}
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// --- 题目生成方法 ---
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private static int getDivisor(int dividend) {
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List<Integer> divisors = new ArrayList<>();
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for (int j = 1; j <= dividend; j++) {
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if (dividend % j == 0) {
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divisors.add(j);
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}
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}
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return divisors.get(rand.nextInt(divisors.size()));
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}
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/**
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* MODIFICATION: 增加答案非负、括号数量和操作数关联的逻辑
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*/
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public static Problem generatePrimaryExpr() {
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Problem problem;
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double result;
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do {
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// 生成 2 到 4 个操作数
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int operands = rand.nextInt(3) + 2;
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List<String> parts = new ArrayList<>();
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for (int i = 0; i < operands; i++) {
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if (i > 0) {
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parts.add(OPS_PRIMARY[rand.nextInt(OPS_PRIMARY.length)]);
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}
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// 仅当操作数 >= 3 时，才有可能生成括号
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if (operands >= 3 && rand.nextBoolean() && i < operands - 1) {
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int num1 = rand.nextInt(50) + 1;
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String innerOp = OPS_PRIMARY[rand.nextInt(OPS_PRIMARY.length)];
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int num2;
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if (innerOp.equals("/")) {
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num2 = getDivisor(num1);
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} else {
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num2 = rand.nextInt(50) + 1;
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}
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parts.add("(" + num1 + " " + innerOp + " " + num2 + ")");
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i++; // 括号表达式计为2个操作数
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} else {
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int num;
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if (i > 0 && parts.get(parts.size() - 1).equals("/")) {
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String dividendStr = parts.get(parts.size() - 2);
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if (dividendStr.startsWith("(")) {
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// 为避免 (a+b)/c 这种复杂情况无法保证整数结果，直接替换运算符
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parts.set(parts.size() - 1, OPS_PRIMARY[rand.nextInt(3)]); // +, -, *
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num = rand.nextInt(100) + 1;
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} else {
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int dividend = Integer.parseInt(dividendStr);
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num = getDivisor(dividend);
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}
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} else {
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num = rand.nextInt(100) + 1;
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}
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parts.add(String.valueOf(num));
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}
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}
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String expression = String.join(" ", parts);
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problem = createProblem(expression);
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result = problem.getResult();
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// 循环直到答案为非负整数
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} while (result < 0 || Double.isNaN(result) || Math.abs(result - Math.round(result)) > 0.0001);
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return problem;
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}
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public static Problem generateMiddleExpr() {
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int operands = rand.nextInt(5) + 1;
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StringBuilder expr = new StringBuilder();
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boolean hasSquareOrSqrt = false;
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for (int i = 0; i < operands; i++) {
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if (i > 0) {
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expr.append(" ").append(OPS_MIDDLE[rand.nextInt(OPS_MIDDLE.length)]).append(" ");
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}
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int num = rand.nextInt(100) + 1;
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if (!hasSquareOrSqrt && rand.nextBoolean()) {
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expr.append(rand.nextBoolean() ? "sqrt(" + num + ")" : num + "^2");
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hasSquareOrSqrt = true;
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} else {
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expr.append(num);
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}
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}
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if (!hasSquareOrSqrt) {
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expr.append(" + ").append(rand.nextInt(50) + 1).append("^2");
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}
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return createProblem(expr.toString());
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}
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public static Problem generateHighExpr() {
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int attempts = 0;
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final int maxAttempts = 10;
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while (attempts < maxAttempts) {
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int operands = rand.nextInt(3) + 2; // 2-4个操作数
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StringBuilder expr = new StringBuilder();
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boolean hasTrig = false;
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for (int i = 0; i < operands; i++) {
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if (i > 0) {
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String[] validOps = {"+", "-", "*", "/"};
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String op = validOps[rand.nextInt(validOps.length)];
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expr.append(" ").append(op).append(" ");
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}
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// 强制至少有一个操作数是三角函数
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if (!hasTrig && (i == operands - 1 || rand.nextBoolean())) {
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String[] funcs = {"sin", "cos", "tan"};
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String func = funcs[rand.nextInt(funcs.length)];
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int angle = rand.nextInt(90) + 1; // 1-90度
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expr.append(func).append("(").append(angle).append(")");
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hasTrig = true;
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} else {
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// 其他操作数可以是普通数字、平方或开方
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int num = rand.nextInt(100) + 1;
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if (rand.nextBoolean() && hasTrig) { // 确保已经有三角函数后再添加其他函数
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if (rand.nextBoolean()) {
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expr.append(num).append("^2");
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} else {
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expr.append("sqrt(").append(num).append(")");
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}
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} else {
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expr.append(num);
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}
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}
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}
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// 如果没有三角函数，强制添加一个
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if (!hasTrig) {
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String[] funcs = {"sin", "cos", "tan"};
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String func = funcs[rand.nextInt(funcs.length)];
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int angle = rand.nextInt(90) + 1;
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if (rand.nextBoolean()) {
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// 在开头添加
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expr.insert(0, func + "(" + angle + ") + ");
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} else {
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// 在结尾添加
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expr.append(" + ").append(func).append("(").append(angle).append(")");
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}
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hasTrig = true;
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}
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String expression = expr.toString();
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// 验证表达式
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Problem problem = createProblem(expression);
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if (problem != null) {
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return problem;
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}
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attempts++;
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System.err.println("生成高中题目失败，尝试次数: " + attempts + ", 表达式: " + expression);
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}
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return createProblem("sin(30) + cos(60)");
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}
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} |
