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| 1 | +// Source : https://leetcode.com/problems/trapping-rain-water/ |
| 2 | +// Author : henrytien |
| 3 | +// Date : 2022年02月02日 |
| 4 | + |
| 5 | +/***************************************************************************************************** |
| 6 | + * |
| 7 | + * Given n non-negative integers representing an elevation map where the width of each bar is 1, |
| 8 | + * compute how much water it can trap after raining. |
| 9 | + * |
| 10 | + * Example 1: |
| 11 | + * |
| 12 | + * Input: height = [0,1,0,2,1,0,1,3,2,1,2,1] |
| 13 | + * Output: 6 |
| 14 | + * Explanation: The above elevation map (black section) is represented by array |
| 15 | + * [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped. |
| 16 | + * |
| 17 | + * Example 2: |
| 18 | + * |
| 19 | + * Input: height = [4,2,0,3,2,5] |
| 20 | + * Output: 9 |
| 21 | + * |
| 22 | + * Constraints: |
| 23 | + * |
| 24 | + * n == height.length |
| 25 | + * 1 <= n <= 2 * 104 |
| 26 | + * 0 <= height[i] <= 105 |
| 27 | + ******************************************************************************************************/ |
| 28 | + |
| 29 | +#include "../inc/ac.h" |
| 30 | +class Solution |
| 31 | +{ |
| 32 | +public: |
| 33 | + int trap(vector<int> &height) |
| 34 | + { |
| 35 | + |
| 36 | + if (height.size() == 0) |
| 37 | + { |
| 38 | + return 0; |
| 39 | + } |
| 40 | + int res = 0; |
| 41 | + int left = 0, right = height.size() - 1; |
| 42 | + int max_left = 0, max_right = 0; |
| 43 | + |
| 44 | + while (left <= right) |
| 45 | + { |
| 46 | + if (height[left] <= height[right]) |
| 47 | + { |
| 48 | + if (height[left] > max_left) |
| 49 | + { |
| 50 | + max_left = height[left]; |
| 51 | + } |
| 52 | + else |
| 53 | + { |
| 54 | + res += max_left - height[left]; |
| 55 | + } |
| 56 | + left++; |
| 57 | + } |
| 58 | + else |
| 59 | + { |
| 60 | + if (height[right] > max_right) |
| 61 | + { |
| 62 | + max_right = height[right]; |
| 63 | + } |
| 64 | + else |
| 65 | + { |
| 66 | + res += max_right - height[right]; |
| 67 | + } |
| 68 | + right--; |
| 69 | + } |
| 70 | + } |
| 71 | + return res; |
| 72 | + } |
| 73 | +}; |
| 74 | + |
| 75 | +int main() |
| 76 | +{ |
| 77 | + |
| 78 | + vector<int> height{0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1}; |
| 79 | + cout << Solution().trap(height); |
| 80 | + return 0; |
| 81 | +} |
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