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!
class Solution {
public:
int trap(vector<int>& height) {
int n=height.size();
int result=;
vector<int> left(n),right(n);
for(int i=;i<n;i++)
{
left[i]=i?max(left[i-],height[i]):height[i];
}
for(int j=n-;j>=;j--)
{
right[j]=(n--j)?max(right[j+],height[j]):height[j];
}
for(int k=;k<n;k++)
{
result+=min(left[k],right[k])-height[k];
}
return result;
}
};