_556.java

package com.fishercoder.solutions;


public class _556 {
    public static class Solution1 {
        /**
         * credit: https://discuss.leetcode.com/topic/85759/this-problem-is-the-same-to-next-permutation-algorithm-only and https://discuss.leetcode.com/topic/85755/java-solution-like-next-permutation-problem-o-n
         */

        public int nextGreaterElement(int n) {
            char[] digits = String.valueOf(n).toCharArray();
            int i = digits.length - 2;
            while (i >= 0 && digits[i + 1] <= digits[i]) {
                i--;
            }
            if (i < 0) {
                return -1;
            }
            int j = digits.length - 1;
            while (j >= 0 && digits[j] <= digits[i]) {
                j--;
            }
            swap(digits, i, j);
            reverse(digits, i + 1);
            try {
                return Integer.parseInt(new String(digits));
            } catch (Exception e) {
                return -1;
            }
        }

        private void reverse(char[] a, int start) {
            int i = start;
            int j = a.length - 1;
            while (i < j) {
                swap(a, i, j);
                i++;
                j--;
            }
        }

        private void swap(char[] a, int i, int j) {
            char temp = a[i];
            a[i] = a[j];
            a[j] = temp;
        }
    }

}