solution.java

class Solution {
    public int maxWater(int arr[]) {
        int n = arr.length;
        if (n <= 2)
            return 0;

        int left = 0, right = n - 1;
        int leftMax = 0, rightMax = 0;
        int water = 0;

        while (left < right) {
            if (arr[left] < arr[right]) {
                if (arr[left] >= leftMax) {
                    leftMax = arr[left];
                } else {
                    water += leftMax - arr[left];
                }
                left++;
            } else {
                if (arr[right] >= rightMax) {
                    rightMax = arr[right];
                } else {
                    water += rightMax - arr[right];
                }
                right--;
            }
        }

        return water;
    }
}