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# Maximum Width Ramp

Given an array `A` of integers, a *ramp* is a tuple `(i, j)` for which `i < j` and `A[i] <= A[j]`.  The width of such a ramp is `j - i`.

Find the maximum width of a ramp in `A`.  If one doesn't exist, return 0.

**Example 1:**

```
Input: [6,0,8,2,1,5]
Output: 4
Explanation: 
The maximum width ramp is achieved at (i, j) = (1, 5): A[1] = 0 and A[5] = 5.
```

**Example 2:**

```
Input: [9,8,1,0,1,9,4,0,4,1]
Output: 7
Explanation: 
The maximum width ramp is achieved at (i, j) = (2, 9): A[2] = 1 and A[9] = 1.
```

**Note:**

1. `2 <= A.length <= 50000`
2. `0 <= A[i] <= 50000`

```java
class Solution {
    public int maxWidthRamp(int[] nums) {
        int n = nums.length;
        int[] rMax = new int[n];
        rMax[n - 1] = nums[n - 1];
        for (int i = n - 2; i >= 0; i--) {
            rMax[i] = Math.max(rMax[i + 1], nums[i]);
        }
        // The trick is that left pointer iterates over original array and right pointer
        // iterates over an array which stores maximum no. on the right for each index.
        int left = 0, right = 0;
        int ans = 0;
        while (right < n) {
            // If item at 'left' index > all the elements [right,n)
            // then it cannot be used in our answer
            while (left < right && nums[left] > rMax[right]) {
                left++;
            }
            ans = Math.max(ans, right - left);
            right++;
        }
        return ans;
    }
}
```