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src/MiddleSchoolProblemGenerator.java

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+// Middleproblem.java
+import java.util.Random;
+
+/**
+ * 初中数学题目生成器实现类。
+ */
+public class MiddleSchoolProblemGenerator implements MathProblemGenerator {
+  private final Random random = new Random();
+  private static int advancedOperationFlag = 1;
+  private String userName = "default";
+  private String timestamp = "default";
+  private int problemNumber = 1;
+
+  public static void main(String[] args) {
+    for (int index = 0; index < 15; index++) {
+      advancedOperationFlag = 1;
+      MiddleSchoolProblemGenerator generator = new MiddleSchoolProblemGenerator();
+      System.out.println((index + 1) + ". " + generator.generateSmartExpression());
+    }
+  }
+
+  public void start(int problemCount, String userName) {
+    this.userName = userName;
+    TimeManager timeManager = new TimeManager();
+    timestamp = timeManager.getCurrentTime();
+
+    for (int index = 0; index < problemCount; index++) {
+      advancedOperationFlag = 1;
+      System.out.println((index + 1) + ". " + generateSmartExpression());
+      System.out.println();
+    }
+  }
+
+  @Override
+  public String generateSmartExpression() {
+    int operatorCount = random.nextInt(3) + 1;
+    int advancedOperationTarget = random.nextInt(operatorCount) + 1;
+    String result;
+
+    while (true) {
+      boolean isDuplicate = false;
+      result = buildExpression(operatorCount, advancedOperationTarget);
+
+      FileManager fileManager = new FileManager();
+      fileManager.readUserFiles(userName);
+
+      for (String line : fileManager.getFileLines()) {
+        String[] parts = line.split("\\.", 2);
+        String expression = parts.length > 1 ? parts[1] : line;
+        if (result.equals(expression)) {
+          isDuplicate = true;
+          break;
+        }
+      }
+
+      if (isDuplicate) {
+        continue;
+      }
+
+      fileManager.createUserFile(userName, timestamp);
+      fileManager.writeToFile(userName, timestamp, problemNumber + "." + result);
+      fileManager.writeToFile(userName, timestamp, " ");
+      problemNumber++;
+      break;
+    }
+    return result;
+  }
+
+  @Override
+  public String buildExpression(int operatorCount, int advancedOperationTarget) {
+    if (operatorCount == 1) {
+      return generateSimpleExpression(advancedOperationTarget);
+    }
+
+    int splitPoint = random.nextInt(operatorCount - 1) + 1;
+
+    String leftPart = (splitPoint > 1 && random.nextBoolean())
+            ? "(" + buildExpression(splitPoint, advancedOperationTarget) + ")"
+            : buildExpression(splitPoint, advancedOperationTarget);
+
+    String rightPart = (operatorCount - splitPoint > 1 && random.nextBoolean())
+            ? "(" + buildExpression(operatorCount - splitPoint, advancedOperationTarget) + ")"
+            : buildExpression(operatorCount - splitPoint, advancedOperationTarget);
+
+    char operator = getRandomOperator("+-*/");
+    return leftPart + " " + operator + " " + rightPart;
+  }
+
+  @Override
+  public String generateSimpleExpression(int advancedOperationTarget) {
+    int firstOperand = random.nextInt(100) + 1;
+    int secondOperand = random.nextInt(100) + 1;
+    char operator = getRandomOperator("+-*/√²");
+
+    if (advancedOperationFlag == advancedOperationTarget) {
+      operator = getRandomOperator("√²");
+      if (operator == '√') {
+        advancedOperationFlag = 0;
+        return operator + "" + secondOperand;
+      } else if (operator == '²') {
+        advancedOperationFlag = 0;
+        return firstOperand + "" + operator;
+      }
+    } else {
+      advancedOperationFlag++;
+    }
+
+    if (random.nextInt(2) == 0) {
+      return firstOperand + "";
+    }
+
+    if (operator == '√') {
+      return operator + "" + secondOperand;
+    } else if (operator == '²') {
+      return firstOperand + "" + operator;
+    } else {
+      if (random.nextBoolean()) {
+        return firstOperand + " " + operator + " " + secondOperand;
+      } else {
+        return "(" + firstOperand + " " + operator + " " + secondOperand + ")";
+      }
+    }
+  }
+
+  @Override
+  public char getRandomOperator(String operators) {
+    return operators.charAt(random.nextInt(operators.length()));
+  }
+}