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package mathpuzzle.service;
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import static mathpuzzle.service.PrimarySchoolGenerator.isNumeric;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.Random;
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/**
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* 高中题目生成器 题目必须包含至少一个 sin, cos, tan 三角函数运算符
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*/
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public class SeniorHighGenerator implements QuestionGenerator {
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private static final String[] TRIG_FUNCS = {"sin", "cos", "tan"};
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private static final String[] OPERATORS = {"+", "-", "*", "/"};
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private final Random random = new Random();
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@Override
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public List<String> generateQuestions(int count) {
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List<String> questions = new ArrayList<>();
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for (int i = 0; i < count; i++) {
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String question = generateSingleQuestion();
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questions.add(question);
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}
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return questions;
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}
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private String generateSingleQuestion() {
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List<String> parts = new ArrayList<>();
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int operandCount = random.nextInt(5) + 1;
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parts = generateBase(operandCount, parts);
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String advancedOp;
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// hasAdvancedOp用以检测下面的循环是否加入了高级运算符，如果没有就启动保底
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if (operandCount == 1) {
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advancedOp = TRIG_FUNCS[random.nextInt(TRIG_FUNCS.length)];
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parts.set(0, advancedOp + parts.get(0));
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} else {
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// 遍历查找左括号的合理位置
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for (int i = 0; i < parts.size(); i++) {
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// 最后一次循环保底生成高中三角函数
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if (i == parts.size() - 1) {
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advancedOp = TRIG_FUNCS[random.nextInt(TRIG_FUNCS.length)];
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parts.set(i, advancedOp + parts.get(i));
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} else if (isNumeric(parts.get(i)) && random.nextBoolean()) {// 随机数看是否为操作数且随即进入生成程序
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// 进入随机生成tan\sin\cos的程序
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parts = generateTrig(parts, i);
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break;
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}
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}
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}
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return String.join(" ", parts) + " =";
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}
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// 产生基本操作
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public List<String> generateBase(int operandCount, List<String> parts) {
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for (int i = 0; i < operandCount; i++) {
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int num = random.nextInt(100) + 1;
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parts.add(String.valueOf(num));
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if (i < operandCount - 1) {
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parts.add(OPERATORS[random.nextInt(OPERATORS.length)]);
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}
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}
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return parts;
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}
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// 产生三角函数运算符
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public List<String> generateTrig(List<String> parts, int i) {
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String trigOp = TRIG_FUNCS[random.nextInt(TRIG_FUNCS.length)];
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if (random.nextBoolean()) {
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parts.set(i, trigOp + parts.get(i));
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} else {
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parts.set(i, trigOp + "(" + parts.get(i));
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// 为避免随机数上限出现0，此处要单独判断一下左括号正好括住倒数第二个操作数的情况
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if (i == parts.size() - 3) {
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parts.set(parts.size() - 1, parts.get(parts.size() - 1) + ")");
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} else {
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while (true) {
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int i2 = random.nextInt(parts.size() - 3 - i) + 2;
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if (isNumeric(parts.get(i + i2))) {
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parts.set(i + i2, parts.get(i + i2) + ")");
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break;
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}
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}
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}
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}
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return parts;
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}
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}
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