From 456e2bbccfe88414130f327071920d1f780ff21c Mon Sep 17 00:00:00 2001
From: LouisFonda <yigencong@yahoo.com>
Date: Mon, 10 Mar 2025 19:35:43 +0800
Subject: [PATCH] =?UTF-8?q?feat:=20leetcode772=EF=BC=8C=E8=AE=A1=E7=AE=97?=
 =?UTF-8?q?=E5=99=A8?=
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---
 recursion/basic-cal.js | 86 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 recursion/basic-cal.js

diff --git a/recursion/basic-cal.js b/recursion/basic-cal.js
new file mode 100644
index 0000000..a90ecb8
--- /dev/null
+++ b/recursion/basic-cal.js
@@ -0,0 +1,86 @@
+/**
+ * LeetCode 772 - Basic Calculator III
+ * Evaluates a string expression containing:
+ * - Numbers (can be multi-digit)
+ * - +, -, *, /
+ * - Parentheses
+ * - Spaces
+ *
+ * @param {string} s - The expression to evaluate
+ * @return {number} - The result of the expression
+ */
+function calculate(s) {
+  let i = 0;
+
+  // 解析表达式
+  function parseExpression() {
+    const stack = [];
+    let num = 0;
+    let sign = '+';
+
+    while (i < s.length) {
+      const char = s[i];
+
+      if (char >= '0' && char <= '9') {
+        // 解析多位数字
+        num = num * 10 + parseInt(char, 10);
+      } else if (char === '(') {
+        // 遇到左括号，获取整个括号的结果，把整个括号看成一个数
+        i++; // Skip the '('
+        num = parseExpression(); // 把整个括号里面的内容看成一个表达式，从括号后一个字符开始处理
+      } else if (char === ')') {
+        // 遇到右括号说明此ParseExpression处理完成，返回整个括号的计算结果给上一个调用
+        updateStack(stack, sign, num);
+        return calculateStack(stack);
+      } else if (char === '+' || char === '-' || char === '*' || char === '/') {
+        // 遇到操作需要把处理好的num压入栈中
+        updateStack(stack, sign, num);
+        sign = char;
+        num = 0;
+      }
+
+      i++;
+    }
+
+    // 将最后一个数字加入栈中
+    updateStack(stack, sign, num);
+
+    // 上面的递归解析过程结束之后会得到一个只包含数字的栈，求和即可
+    return calculateStack(stack);
+  }
+
+  /**
+   *
+   * @param {number[]} stack 收集数字的栈
+   * @param {*} sign - 数字之前的符号
+   * @param {*} num - 要处理的数字
+   * @description 如果数字的前面是乘除法，就把栈顶元素弹出计算过后作为整体压入栈中；是减法就把这个数改成负数，加法就直接压入栈中
+   */
+  function updateStack(stack, sign, num) {
+    if (sign === '+') {
+      stack.push(num);
+    } else if (sign === '-') {
+      stack.push(-num);
+    } else if (sign === '*') {
+      stack.push(stack.pop() * num);
+    } else if (sign === '/') {
+      // 数字前面的操作符如果是除号，需要向下取整
+      const prev = stack.pop();
+      const result = prev / num;
+      stack.push(prev > 0 ? Math.floor(result) : Math.ceil(result));
+    }
+  }
+
+  // 对整个栈求和
+  function calculateStack(stack) {
+    return stack.reduce((sum, num) => sum + num, 0);
+  }
+
+  return parseExpression();
+}
+
+// 测试用例
+console.log(calculate('1+1')); // 2
+console.log(calculate('6-4/2')); // 4
+console.log(calculate('2*(5+5*2)/3+(6/2+8)')); // 21
+console.log(calculate('(2+6*3+5-(3*14/7+2)*5)+3')); // -12