Trapping_rain_water.java

class GFG{

// Function to return the maximum
// water that can be stored
public static int maxWater(int[] arr, int n)
{

    // To store the maximum water
    // that can be stored
    int res = 0;

    // For every element of the array
    // except first and last element
    for(int i = 1; i < n - 1; i++)
    {

        // Find maximum element on its left
        int left = arr[i];
        for(int j = 0; j < i; j++)
        {
            left = Math.max(left, arr[j]);
        }

        // Find maximum element on its right
        int right = arr[i];
        for(int j = i + 1; j < n; j++)
        {
            right = Math.max(right, arr[j]);
        }

        // Update maximum water value
        res += Math.min(left, right) - arr[i];
    }
    return res;
}

// Driver code
public static void main(String[] args)
{
    int[] arr = { 0, 1, 0, 2, 1, 0,
                  1, 3, 2, 1, 2, 1 };
    int n = arr.length;

    System.out.print(maxWater(arr,n));
}
}