partner_program/src/main/java/com/example/myapp/service/MiddleQueSeting.java

// MiddleQueSeting.java
package com.example.myapp.service;

import com.example.myapp.model.Expression;

public class MiddleQueSeting extends AbstractQuestionSeting {

  public Expression applyUnary(Expression child, String op) {
    switch (op) {
      case "²":
        if (child.mainOperator == null) {
          return new Expression(child.expression + "²", child.value * child.value, "²");
        }
        return new Expression("(" + child.expression + ")²", child.value * child.value, "²");
      case "√":
        // 使用适合开方的数（主要是完全平方数）
        String numStr = getNumberForSqrt();
        child = new Expression(numStr, parseNumber(numStr), null);

        double sqrtValue = Math.sqrt(child.value);
        if (child.mainOperator == null) {
          return new Expression("√" + child.expression, sqrtValue, "√");
        }
        return new Expression("√(" + child.expression + ")", sqrtValue, "√");
      default:
        return child;
    }
  }

  @Override
  public String addParenthesesIfNeeded(Expression child, String parentOp, boolean isRightChild) {
    if (child.mainOperator == null || child.mainOperator.equals("²") || child.mainOperator.equals("√")) {
      return child.expression;
    }

    int parentPriority = getPriority(parentOp);
    int childPriority = getPriority(child.mainOperator);

    if (childPriority < parentPriority) {
      return "(" + child.expression + ")";
    }

    if (isRightChild && (parentOp.equals("-") || parentOp.equals("/"))) {
      if (parentPriority == childPriority) {
        return "(" + child.expression + ")";
      }
    }

    return child.expression;
  }

  @Override
  public Expression setQuestion(int count) {
    Expression result = firstSetQuestion(count);
    // 确保初中题目包含平方或开方
    while (!result.expression.contains("²") && !result.expression.contains("√")) {
      result = firstSetQuestion(count);
    }
    return result;
  }

  public Expression firstSetQuestion(int count) {
    if (count == 1) {
      String numStr = getRandomNumber();
      Expression expr = new Expression(numStr, parseNumber(numStr), null);
      return probability(expr);
    }
    int leftCount = 1 + rand.nextInt(count - 1);
    int rightCount = count - leftCount;
    Expression left = firstSetQuestion(leftCount);
    Expression right = firstSetQuestion(rightCount);
    String op = getRandomOperator();
    double value = 0;
    switch (op) {
      case "+":
        value = left.value + right.value;
        break;
      case "-":
        value = left.value - right.value;
        if (value < 0) {
          Expression temp = left;
          left = right;
          right = temp;
          value = left.value - right.value;
        }
        break;
      case "*":
        value = left.value * right.value;
        break;
      case "/":
        if (Math.abs(right.value) < 1e-10) {
          right = firstSetQuestion(rightCount);
        }
        value = left.value / right.value;
        break;
    }
    String leftExpr = addParenthesesIfNeeded(left, op, false);
    String rightExpr = addParenthesesIfNeeded(right, op, true);
    Expression result = new Expression(leftExpr + " " + op + " " + rightExpr, value, op);
    result = probability(result);
    return result;
  }

  public Expression probability(Expression result) {
    if (rand.nextDouble() < 0.3) {
      String[] unaryOps = {"²", "√"};
      String unaryOp = unaryOps[rand.nextInt(unaryOps.length)];
      result = applyUnary(result, unaryOp);
      result.mainOperator = unaryOp;
    }
    return result;
  }
}