ADD file via upload

src/TrigManager.java

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+import java.util.List;
+import java.util.Random;
+
+/**
+ * 负责添加三角函数
+ */
+public class TrigManager {
+  private static final Random RANDOM = new Random();
+  private static final String[] TRIG_FUNCTIONS = {"sin", "cos", "tan"};
+  
+  //添加三角函数
+  public String addTrigOperations(String expression, List<Integer> numPositions) {
+    if (numPositions.isEmpty()) {
+      return expression;
+    }
+    
+    String[] tokens = expression.split(" ");
+    int targetIndex = chooseTargetIndex(numPositions, tokens);
+    if (targetIndex == -1) {
+      return expression;
+    }
+    
+    tokens[targetIndex] = applyTrig(tokens[targetIndex]);
+    return String.join(" ", tokens);
+  }
+  
+  //随机函数种类
+  private int chooseTargetIndex(List<Integer> numPositions, String[] tokens) {
+    for (int tries = 0; tries < 50; tries++) {
+      int idx = numPositions.get(RANDOM.nextInt(numPositions.size()));
+      if (canApplyTrig(tokens, idx)) {
+        return idx;
+      }
+    }
+    return -1;
+  }
+  
+  //检测三角函数是否合法
+  private boolean canApplyTrig(String[] tokens, int index) {
+    if (!isNumber(tokens[index])) {
+      return false;
+    }
+    int value = Integer.parseInt(tokens[index]);
+    
+    // 防止 tan(90)
+    if (value == 90 && RANDOM.nextInt(3) == 2) {
+      return false;
+    }
+    // cos(90) 不加在除法右边
+    if (index > 0 && tokens[index - 1].equals("/") && value == 90) {
+      return false;
+    }
+    return true;
+  }
+  
+  //添加操作
+  private String applyTrig(String token) {
+    String func = TRIG_FUNCTIONS[RANDOM.nextInt(TRIG_FUNCTIONS.length)];
+    return func + "(" + token + ")";
+  }
+  
+  private boolean isNumber(String token) {
+    try {
+      Integer.parseInt(token);
+      return true;
+    } catch (NumberFormatException e) {
+      return false;
+    }
+  }
+}