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package com.mathapp.problemGenerators;
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import com.mathapp.models.Equation;
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import com.mathapp.models.Operator;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* 高中题目生成器（最终修正版）。
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* 采用更稳健的“追加”策略，从根本上避免所有索引越界和除零错误。
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*/
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public class HighSchoolProblemGenerator extends MiddleSchoolProblemGenerator {
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private static final int[] PREDEFINED_ANGLES = {0, 30, 45, 60, 90};
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private static final String[] TRIG_FUNCTIONS = {"sin", "cos", "tan"};
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@Override
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protected Equation createProblem() {
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// 1. 调用父类方法生成一个包含平方或开方的基础题目
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Equation middleSchoolEquation = super.createProblem();
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List<String> operands = new ArrayList<>(middleSchoolEquation.operands());
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List<Operator> operators = new ArrayList<>(middleSchoolEquation.operators());
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String trigExpression;
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Operator connectingOperator;
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// 2.【最终修正策略】使用健壮性检查循环，直到生成一个绝对安全的组合
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while (true) {
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// 2a. 生成三角函数部分，并确保它不是 tan(90°)
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String function;
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int angleInDegrees;
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do {
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function = TRIG_FUNCTIONS[random.nextInt(TRIG_FUNCTIONS.length)];
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angleInDegrees = PREDEFINED_ANGLES[random.nextInt(PREDEFINED_ANGLES.length)];
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} while (function.equals("tan") && angleInDegrees == 90);
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trigExpression = String.format("%s(%s)", function, getRadianString(angleInDegrees));
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// 2b. 随机选择一个连接运算符
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connectingOperator = Operator.values()[random.nextInt(Operator.values().length)];
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// 2c.【健壮性检查】检查这个新运算符是否会与三角函数的值构成除零错误
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boolean isTrigValueZero = (function.equals("sin") && angleInDegrees == 0) ||
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(function.equals("tan") && angleInDegrees == 0);
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// 如果新运算符是除法，且三角函数的值是0，则这是一个非法组合，必须重试
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if (connectingOperator == Operator.DIVIDE && isTrigValueZero) {
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continue; // 非法组合，重新循环
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}
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// 如果代码能执行到这里，说明组合是安全的，可以退出循环
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break;
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}
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// 3.【安全的追加操作】将生成的安全组合追加到表达式末尾
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// 这种方法永远不会导致 IndexOutOfBoundsException
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operands.add(trigExpression);
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operators.add(connectingOperator);
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return new Equation(operands, operators);
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}
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/**
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* 将特殊的角度值转换为 exp4j 可以计算的、基于 pi 的弧度字符串。
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*/
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private String getRadianString(int angleInDegrees) {
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switch (angleInDegrees) {
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case 0: return "0";
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case 30: return "pi/6";
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case 45: return "pi/4";
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case 60: return "pi/3";
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case 90: return "pi/2";
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default: return "0";
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}
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}
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} |
