ADD file via upload

src/ExpressionBuilder.java

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+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+
+public class ExpressionBuilder {
+  private static final Random RANDOM = new Random();
+  private static final String[] OPERATORS = {"+", "-", "*", "/"};
+  
+  // 生成基础四则运算表达式
+  public String generateBasicExpression(int count) {
+    StringBuilder sb = new StringBuilder();
+    for (int i = 0; i < count; i++) {
+      sb.append(RANDOM.nextInt(100) + 1);
+      if (i < count - 1) {
+        sb.append(" ").append(OPERATORS[RANDOM.nextInt(OPERATORS.length)]).append(" ");
+      }
+    }
+    return sb.toString();
+  }
+  
+  // 获取表达式中数字的位置
+  public List<Integer> getNumberPositions(String expression) {
+    String[] tokens = expression.split(" ");
+    List<Integer> positions = new ArrayList<>();
+    for (int i = 0; i < tokens.length; i++) {
+      if (isNumber(tokens[i])) positions.add(i);
+    }
+    return positions;
+  }
+  
+  // 检查是否存在除零
+  public boolean hasDivideByZero(String expression) {
+    String[] tokens = expression.split(" ");
+    for (int i = 0; i < tokens.length - 1; i++) {
+      if (tokens[i].equals("/")) {
+        try {
+          if (Integer.parseInt(tokens[i + 1]) == 0) return true;
+        } catch (NumberFormatException e) {
+          //
+        }
+      }
+    }
+    return false;
+  }
+  
+  //判断是否为数字位
+  private boolean isNumber(String token) {
+    try { Integer.parseInt(token); return true; }
+    catch (NumberFormatException e) { return false; }
+  }
+}