feat: 算法-二分与回溯

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+.vscode/

source/_posts/算法-二分与回溯.md

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+---
+title: 算法-二分与回溯
+date: 2024-08-19 22:53:44
+categories:
+  - 数据结构与算法
+tags:
+  - js
+  - 算法
+cover: https://assets.leetcode.cn/aliyun-lc-upload/uploaded_files/2021/03/73c9f099-abbe-4d94-853f-f8abffd459cd/leetcode.png
+---
+
+**二分和回溯在代码书写上是有明确的公式的。**
+
+## 二分
+
+前提：有序数组
+思想：判断中间位置的值大小，对半分去找
+
+```js
+function search(arr, target) {
+  let low = 0, high = arr.length - 1
+  while(low <= high) {
+    let mid = low + ((high - low) >> 1)
+    if(arr[mid] === target) {
+      return mid;
+    }else if(arr[mid]<target){
+      low = mid + 1;
+    } else {
+      high = mid -1;
+    }
+  }
+  return -1;
+}
+```
+
+【相关题库】：https://leetcode.cn/tag/binary-search/problemset/
+【经典题目】：
+求平方根 - https://leetcode.cn/problems/sqrtx/description/
+寻找旋转排序数组中的最小值 - https://leetcode.cn/problems/find-minimum-in-rotated-sorted-array/description/
+
+## 回溯
+
+```js
+function combine(n, k) {
+  let result = [], path = []
+
+  function backTrace() {
+    // 停止条件
+    if(condition) {
+      result.push([...path]);
+      return;
+    }
+
+    // 尝试一个，然后去掉这个尝试，进行下一轮
+    for(condition) {
+      path.push(i);
+      backTrace();
+      path.pop();
+    }
+  }
+
+  backTrace();
+  return result;
+}
+```
+
+【相关题库】：https://leetcode.cn/tag/backtracking/problemset/
+【经典题目】：
+组合 - https://leetcode.cn/problems/combinations/description/
+组合总数 - https://leetcode.cn/problems/combination-sum/description/
+组合总数2 - https://leetcode.cn/problems/combination-sum-ii/description/
+全排列 - https://leetcode.cn/problems/permutations/description/
+全排列2 - https://leetcode.cn/problems/permutations-ii/description/