Monotone Increasing Digits

Given a non-negative integer N, find the largest number that is less than or equal to N with monotone increasing digits.

(Recall that an integer has monotone increasing digits if and only if each pair of adjacent digits x and y satisfy x <= y.)

Example 1:

Input: N = 10
Output: 9

Example 2:

Input: N = 1234
Output: 1234

Example 3:

Input: N = 332
Output: 299

Note: N is an integer in the range [0, 10^9].

class Solution {
    public int monotoneIncreasingDigits(int N) {
        char[] arrN = String.valueOf(N).toCharArray();
        int monotoneIncreasingToTheLeftOf = arrN.length - 1;
        for (int i = arrN.length - 1; i > 0; i--) {
            if (arrN[i] < arrN[i - 1]) {
                monotoneIncreasingToTheLeftOf = i - 1;
                arrN[i - 1]--;
            }
        }
        for (int i = monotoneIncreasingToTheLeftOf + 1; i < arrN.length; i++)
            arrN[i] = '9';
        return Integer.parseInt(new String(arrN));
    }
}