feat(leecode): 42.接雨水

docs/10.LeeCode/42.接雨水.md

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+---
+title: 42.接雨水
+date: 2024-03-20
+lang: 'zh-CN'
+sidebar: 'auto'
+categories:
+  - LeeCode
+tags:
+location: HangZhou
+---
+
+# Heading
+
+[[toc]]
+
+[42.接雨水](https://leetcode.cn/problems/trapping-rain-water/description/)
+
+Tags: algorithms amazon apple bloomberg google twitter zenefits array two-pointers stack
+
+Langs: c cpp csharp dart elixir erlang golang java javascript kotlin php python python3 racket ruby rust scala swift typescript
+
+- algorithms
+- Hard (63.28%)
+- Likes: 5071
+- Dislikes: -
+- Total Accepted: 901.1K
+- Total Submissions: 1.4M
+- Testcase Example: '[0,1,0,2,1,0,1,3,2,1,2,1]'
+
+<p>给定&nbsp;<code>n</code> 个非负整数表示每个宽度为 <code>1</code> 的柱子的高度图，计算按此排列的柱子，下雨之后能接多少雨水。</p>
+
+<p>&nbsp;</p>
+
+<p><strong>示例 1：</strong></p>
+
+<p><img src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2018/10/22/rainwatertrap.png" style="height: 161px; width: 412px;" /></p>
+
+<pre>
+<strong>输入：</strong>height = [0,1,0,2,1,0,1,3,2,1,2,1]
+<strong>输出：</strong>6
+<strong>解释：</strong>上面是由数组 [0,1,0,2,1,0,1,3,2,1,2,1] 表示的高度图，在这种情况下，可以接 6 个单位的雨水（蓝色部分表示雨水）。 
+</pre>
+
+<p><strong>示例 2：</strong></p>
+
+<pre>
+<strong>输入：</strong>height = [4,2,0,3,2,5]
+<strong>输出：</strong>9
+</pre>
+
+<p>&nbsp;</p>
+
+<p><strong>提示：</strong></p>
+
+<ul>
+	<li><code>n == height.length</code></li>
+	<li><code>1 &lt;= n &lt;= 2 * 10<sup>4</sup></code></li>
+	<li><code>0 &lt;= height[i] &lt;= 10<sup>5</sup></code></li>
+</ul>
+
+<<< @/src/LeeCode/42.接雨水.js
+<<< @/src/LeeCode/42.接雨水1.js

src/LeeCode/42.接雨水.js

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+/*
+ * @lc app=leetcode.cn id=42 lang=javascript
+ *
+ * [42] 接雨水
+ * 乱七八糟解出来的……，固定左指针寻找下一个右侧边际
+ */
+
+// @lc code=start
+/**
+ * @param {number[]} height
+ * @return {number}
+ */
+var trap = function (height) {
+  let i = 0
+  let j = 0
+  let sum = 0
+
+  while (i < height.length) {
+    if (height[i] > 0) {
+      j = i + 1
+      let tmpHeight = 0
+      let tmpMax = 0
+      let rightIndex = 0
+      while (j < height.length && height[j] < height[i]) {
+        if (height[j] > tmpMax) {
+          tmpMax = height[j]
+          rightIndex = j
+        }
+        tmpHeight += height[j++]
+      }
+      if (j < height.length) {
+        rightIndex = j
+      } else if (rightIndex > 0) {
+        let k = rightIndex
+        while (k < j) {
+          tmpHeight -= height[k++]
+        }
+      }
+
+      if (rightIndex > 0) {
+        sum += (rightIndex - i - 1) * Math.min(height[i], height[rightIndex]) - tmpHeight
+        i = rightIndex
+        continue
+      }
+    }
+    i++
+  }
+  return sum
+}
+// @lc code=end

src/LeeCode/42.接雨水1.js

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+/*
+ * @lc app=leetcode.cn id=42 lang=javascript
+ *
+ * [42] 接雨水
+ * 双指针
+ */
+
+// @lc code=start
+/**
+ * @param {number[]} height
+ * @return {number}
+ */
+var trap = function (height) {
+  let left = 0
+  let right = height.length - 1
+  let leftMax = 0
+  let rightMax = 0
+  let sum = 0
+  while (left < right) {
+    leftMax = Math.max(leftMax, height[left])
+    rightMax = Math.max(rightMax, height[right])
+
+    if (height[left] < height[right]) {
+      sum += leftMax - height[left++]
+    } else {
+      sum += rightMax - height[right--]
+    }
+  }
+  return sum
+}
+// @lc code=end