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.
LeetCode[Array]: Trapping Rain Water
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!
int trap(int A[], int n) {
int water = ;
for (int left = , right = n - ; left < right; )
{
int leftHeight = A[left ];
int rightHeight = A[right];
if (leftHeight < rightHeight)
while (left < right && A[++left ] <= leftHeight ) water += (leftHeight - A[left ]);
else
while (left < right && A[--right] <= rightHeight) water += (rightHeight - A[right]);
}
return water;
}