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```// Efficient Method : Time Complexity : O(n), Auxilliary Space : O(n)

import java.util.*;
import java.io.*;

class GFG
{
static int getWater(int arr[], int n)
{
int res = 0;

int lMax[] = new int[n];
int rMax[] = new int[n];

lMax[0] = arr[0];
for(int i = 1; i < n; i++)
lMax[i] = Math.max(arr[i], lMax[i - 1]);

rMax[n - 1] = arr[n - 1];
for(int i = n - 2; i >= 0; i--)
rMax[i] = Math.max(arr[i], rMax[i + 1]);

for(int i = 1; i < n - 1; i++)
res = res + (Math.min(lMax[i], rMax[i]) - arr[i]);

return res;
}

public static void main(String args[])
{
int arr[] = {5, 0, 6, 2, 3}, n = 5;

System.out.println( getWater(arr, n)); // Output : 6
}
}

// Naive Method : Time Complexity : O(n^2)

static int getWater(int arr[], int n)
{
int res = 0;

for(int i = 1; i < n - 1; i++)
{
int lMax = arr[i];

for(int j = 0; j < i; j++)
lMax = Math.max(lMax, arr[j]);

int rMax = arr[i];

for(int j = i + 1; j < n; j++)
rMax = Math.max(rMax, arr[j]);

res = res + (Math.min(lMax, rMax) - arr[i]);
}

return res; // Output : 6
}```