IEEE CodeBuddy | Week 5 | Aditya A & Akash Nair

rain_water.cpp

int Solution::trap(const vector<int> &A) {
    int ans = 0;
    int n = A.size();
    int i = 0, j = n - 1;
    int lm = -1, rm = -1;
    while(i < j){
        if(A[i] < A[j]){
            if(A[i] > lm)   lm = A[i];
            else    ans += (lm - A[i]);
            i++;
        }
        else{
            if(A[j] > rm)   rm = A[j];
            else    ans += (rm - A[j]);
            j--;
        }
    }
    return ans;
}