Trapping Rain Water
Desicription
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.
The above elevation map is represented by array [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. Thanks Marcos for contributing this image!
Solution
代码语言：javascript复制class Solution {
public:
int trap(vector<int>& height) {
if(!height.size())
return 0;
int left = 0;
int right = height.size()-1;
int left_max = height[left];
int right_max = height[right];
int res = 0;
while(left <= right){
if(height[left] <= height[right]){
if(height[left] > left_max)
left_max = height[left];
else
res = left_max - height[left];
left ;
}
else{
if(height[right] > right_max)
right_max = height[right];
else
res = right_max - height[right];
right--;
}
}
return res;
}
};
