Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining.
Example 1:
Input: height = [0,1,0,2,1,0,1,3,2,1,2,1] Output: 6 Explanation: The above elevation map (black section) 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.
Example 2:
Input: height = [4,2,0,3,2,5] Output: 9
Constraints:
n == height.length
1 <= n <= 2 * 104
0 <= height[i] <= 105
- code
class Solution {
public int trap(int[] height) {
int left = 0, right = height.length - 1;
int leftMax = 0, rightMax = 0;
int res = 0;
while (left < right){
if (height[left] > leftMax) leftMax = height[left];
if (height[right] > rightMax) rightMax = height[right];
if (leftMax < rightMax){
res += leftMax - height[left];
left++;
}else{
res += rightMax - height[right];
right--;
}
}
return res;
}
}