p42

发表于 | 分类于 |

LeetCode p42 Trapping Rain Water 题解

1.题目：

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.

For example,
Given [0,1,0,2,1,0,1,3,2,1,2,1], return 6.

题意：

给你一个数组，是每个坐标上砖块的高度，为这组砖块最多可以盛多少水。

2.解题思路:

两个指针，分别从左右出发，原理类似于俄罗斯方块，慢慢消掉被堆满的底层~
具体见代码。

3.代码

[title] [] [url] [link text]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
 
public class Solution {
    public int trap(int[] height) {
        if (height.length < 3)
			return 0;
		int l = 0;
		int r = height.length - 1;
		int ans = 0;
		int last = 0;
		while (l < r) {
			int min = Math.min(height[l], height[r]);
			for (int i = l + 1; i < r; i++) {
				if (min == last)
					break;
				if (height[i] < min) {
					if (height[i] < last) {
						ans += min - last;
					} else {
						ans += min - height[i];
					}
				
				}
			}
		
			last = min;
			if (min == height[l]) {
				do {
					l++;

				} while (l < r && height[l] <= min);
			} else {
				do {
					r--;

				} while (l < r && height[r] <= min);
			}
		}

		return ans;
    }
}

4.一些总结：