Arrays_Trapping_Rainwater.cpp

#include <iostream>
using namespace std;

int trappingWater(int arr[], int n)
{

    int lmax[n];
    lmax[0] = arr[0];
    for (int i = 1; i < n; i++)
    {
        int temp = max(arr[i], lmax[i - 1]);
        lmax[i] = temp;
    }

    int rmax[n];
    rmax[n - 1] = arr[n - 1];
    for (int i = n - 2; i >= 0; i--)
    {
        int temp = max(arr[i], rmax[i + 1]);
        rmax[i] = temp;
    }

    int water = 0;
    for (int i = 1; i < n - 1; i++)
    {
        water += min(lmax[i], rmax[i]) - arr[i];
    }

    return water;
}

int main()
{

    int n;

    cin >> n;

    int a[n];

    for (int i = 0; i < n; i++)
    {
        cin >> a[i];
    }

    cout << trappingWater(a, n) << endl;

    return 0;
}