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package service;
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import model.Question;
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import java.util.List;
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import java.util.ArrayList;
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import java.util.Stack;
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public class PrimaryQuestionGenerator extends AbstractQuestionGenerator {
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private static final String[] OPERATORS = {"+", "-" , "×", "÷"};
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public PrimaryQuestionGenerator() {
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super("小学");
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}
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@Override
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public Question generateQuestion() {
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int operandCount = random.nextInt(4) + 2; // 2-5个操作数
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List<Integer> operands = new ArrayList<>();
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List<String> operators = new ArrayList<>();
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// 生成操作数和运算符，确保结果为非负整数
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boolean valid = false;
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String content = "";
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int answer = 0;
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int attempts = 0;
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int maxAttempts = 100; // 添加最大尝试次数
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while (!valid && attempts < maxAttempts) {
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attempts++; // 计数
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operands.clear();
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operators.clear();
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// 生成操作数
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for (int i = 0; i < operandCount; i++) {
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operands.add(getRandomOperand());
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}
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// 生成运算符，限制最多只有一个除法
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boolean hasDivision = false;
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for (int i = 0; i < operandCount - 1; i++) {
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String op;
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// 如果已经有除法了，就只生成其他运算符
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if (hasDivision) {
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String[] otherOperators = {"+", "-", "×"};
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op = getRandomOperator(otherOperators);
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} else {
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op = getRandomOperator(OPERATORS);
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if (op.equals("÷")) {
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hasDivision = true;
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// 确保除法能整除：调整被除数
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int divisor = operands.get(i + 1);
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int dividend = operands.get(i);
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// 如果当前不能整除，调整被除数
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if (divisor == 0 || dividend % divisor != 0) {
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// 如果除数为0，重新生成除数
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if (divisor == 0) {
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divisor = random.nextInt(9) + 2; // 2-10
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operands.set(i + 1, divisor);
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}
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// 调整被除数为除数的倍数
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int multiple = random.nextInt(3) + 1; // 1-3倍
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operands.set(i, divisor * multiple);
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}
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}
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}
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operators.add(op);
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}
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content = buildPrimaryContent(operands, operators);
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answer = calculateExpression(content);
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valid = answer >= 0; // 验证答案是否非负整数
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}
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// 如果多次尝试都失败，生成一个简单的保底题目
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if (!valid) {
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return generateSimpleQuestion();
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}
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OptionsResult options = generateOptions(answer);
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return new Question(content, options, options.getCorrectIndex(), difficulty);
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}
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// 生成简单的保底题目
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private Question generateSimpleQuestion() {
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int a = random.nextInt(10) + 5; // 5-14
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int b = random.nextInt(5) + 1; // 1-5
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String[] simpleOps = {"+", "×"};
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String op = simpleOps[random.nextInt(simpleOps.length)];
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String content;
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int answer;
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if (op.equals("+")) {
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content = a + " + " + b + " = ?";
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answer = a + b;
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} else {
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content = a + " × " + b + " = ?";
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answer = a * b;
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}
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OptionsResult options = generateOptions(answer);
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return new Question(content, options, options.getCorrectIndex(), difficulty);
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}
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private String buildPrimaryContent(List<Integer> operands, List<String> operators) {
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StringBuilder content = new StringBuilder();
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// 随机决定是否加括号（只在有3个及以上操作数时）
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boolean useParentheses = random.nextDouble() < 0.6 && operands.size() > 2;
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if (useParentheses) {
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// 随机决定括号包含的操作数数量（至少2个，最多 operands.size()-1 个）
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int parenLength = random.nextInt(operands.size() - 1) + 2;
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// 随机决定括号的起始位置
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int start = random.nextInt(operands.size() - parenLength + 1);
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int end = start + parenLength - 1;
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for (int i = 0; i < operands.size(); i++) {
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if (i == start) {
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content.append("(");
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}
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content.append(operands.get(i));
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if (i == end) {
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content.append(")");
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}
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if (i < operators.size()) {
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content.append(" ").append(operators.get(i)).append(" ");
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}
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}
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} else {
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for (int i = 0; i < operands.size(); i++) {
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content.append(operands.get(i));
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if (i < operators.size()) {
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content.append(" ").append(operators.get(i)).append(" ");
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}
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}
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}
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content.append(" = ?");
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return content.toString();
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}
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private int calculateExpression(String expression) {
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try {
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// 移除 "= ?" 部分
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String mathExpr = expression.replace(" = ?", "").trim();
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return evaluate(mathExpr);
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} catch (Exception e) {
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return -1; // 计算失败
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}
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}
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private int evaluate(String expression) {
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Stack<Integer> numbers = new Stack<>();
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Stack<Character> ops = new Stack<>();
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for (int i = 0; i < expression.length(); i++) {
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char c = expression.charAt(i);
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if (c == ' ') {
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continue; // 跳过空格
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}
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if (Character.isDigit(c)) {
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// 读取完整数字
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int num = 0;
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while (i < expression.length() && Character.isDigit(expression.charAt(i))) {
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num = num * 10 + (expression.charAt(i) - '0');
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i++;
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}
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i--;
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numbers.push(num);
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} else if (c == '(') {
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ops.push(c);
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} else if (c == ')') {
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// 计算括号内的所有运算
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while (ops.peek() != '(') {
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int result = applyOp(ops.pop(), numbers.pop(), numbers.pop());
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if (result < 0) return -1; // 检查中间结果是否负数
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numbers.push(result);
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}
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ops.pop(); // 弹出 '('
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} else if (isOperator(c)) {
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// 处理运算符优先级：如果栈顶运算符优先级更高或相等，先计算栈顶的
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while (!ops.isEmpty() && hasPrecedence(ops.peek(), c)) {
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int result = applyOp(ops.pop(), numbers.pop(), numbers.pop());
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if (result < 0) return -1; // 检查中间结果是否负数
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numbers.push(result);
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}
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ops.push(c);
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}
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}
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// 计算剩余表达式
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while (!ops.isEmpty()) {
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int result = applyOp(ops.pop(), numbers.pop(), numbers.pop());
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if (result < 0) return -1; // 检查中间结果是否负数
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numbers.push(result);
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}
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return numbers.pop();
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}
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private boolean hasPrecedence(char op1, char op2) {
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if (op1 == '(' || op1 == ')') {
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return false;
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}
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// op1是栈顶运算符，op2是当前运算符
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// 如果栈顶运算符优先级高于或等于当前运算符，返回true（先计算栈顶的）
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if ((op1 == '×' || op1 == '÷') && (op2 == '+' || op2 == '-')) {
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return true;
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}
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// 同级运算符从左到右计算
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if ((op1 == '+' || op1 == '-') && (op2 == '+' || op2 == '-')) {
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return true;
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}
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if ((op1 == '×' || op1 == '÷') && (op2 == '×' || op2 == '÷')) {
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return true;
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}
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return false;
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}
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private boolean isOperator(char c) {
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return c == '+' || c == '-' || c == '×' || c == '÷';
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}
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private int applyOp(char op, int b, int a) {
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switch (op) {
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case '+':
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return a + b;
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case '-':
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int result = a - b;
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return result >= 0 ? result : -1; // 确保非负
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case '×':
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return a * b;
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case '÷':
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if (b == 0 || a % b != 0) {
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return -1; // 除数为0或不整除
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}
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return a / b;
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default:
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return -1;
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}
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}
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} |
