From 2405f03d94320d195c97e9719853297d5373aeaf Mon Sep 17 00:00:00 2001
From: ironartisan <ironerhalo@gmail.com>
Date: Tue, 17 Aug 2021 11:21:23 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A00042.=E6=8E=A5=E9=9B=A8?=
 =?UTF-8?q?=E6=B0=B4java=E5=8A=A8=E6=80=81=E8=A7=84=E5=88=92=E8=A7=A3?=
 =?UTF-8?q?=E6=B3=95?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 problems/0042.接雨水.md | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/problems/0042.接雨水.md b/problems/0042.接雨水.md
index c241b441..22c8c0ef 100644
--- a/problems/0042.接雨水.md
+++ b/problems/0042.接雨水.md
@@ -365,6 +365,7 @@ public:
 ## 其他语言版本 
 
 Java: 
+
 双指针法
 ```java
 class Solution {
@@ -390,6 +391,33 @@ class Solution {
     }
 }
 ```
+动态规划法
+```java
+class Solution {
+    public int trap(int[] height) {
+        int length = height.length;
+        if (length <= 2) return 0;
+        int[] maxLeft = new int[length];
+        int[] maxRight = new int[length];
+        
+        // 记录每个柱子左边柱子最大高度
+        maxLeft[0] = height[0];
+        for (int i = 1; i< length; i++) maxLeft[i] = Math.max(height[i], maxLeft[i-1]);
+        
+        // 记录每个柱子右边柱子最大高度
+        maxRight[length - 1] = height[length - 1];
+        for(int i = length - 2; i >= 0; i--) maxRight[i] = Math.max(height[i], maxRight[i+1]);
+        
+        // 求和
+        int sum = 0;
+        for (int i = 0; i < length; i++) {
+            int count = Math.min(maxLeft[i], maxRight[i]) - height[i];
+            if (count > 0) sum += count;
+        }
+        return sum;
+    }
+}
+```
 Python:
 
 双指针法