Trapping Rain Water.cpp

class Solution {
public:
    int trap(vector<int>& height) {
        
        int n = height.size(); 
        int left=0; int right=n-1;
        int res=0;
        int maxleft=0, maxright=0;
        
        while(left<=right){
            
            if(height[left]<=height[right]){

                if(height[left]>=maxleft) maxleft=height[left];
                else res+=maxleft-height[left];
                
                left++;
            }
            else{

                if(height[right]>=maxright) maxright= height[right];
                else res+=maxright-height[right];
                
                right--;
            }
        }
        return res;
    }
};