[leetcode] Plus One

Given a non-negative number represented as an array of digits, plus one to the number.

The digits are stored such that the most significant digit is at the head of the list.

package com.wyt.leetcodeOJ;

import java.util.Arrays;

public class PlusOne {

	public static void main(String[] args) {
		int[] digits = {9,9};
		System.out.println(Arrays.toString(plusOne(digits)));
	}
	
	public static int[] plusOne(int[] digits) {
		if(digits == null || digits.length == 0) {
			return digits;
		}
		
		int len = digits.length;
		if(digits[len - 1] < 9) {
			digits[len - 1] ++;
			return digits;
		}
		
		if(len == 1) {
			digits = new int[2];
			digits[0] = 1;
			digits[1] = 0;
			return digits;
		} else {
			int k = len;
			digits[len - 1] = 0;
			for (int i = len - 2; i >= 0; i--) {
				if(digits[i] < 9) {
					digits[i]++;
					break;
				} else {
					digits[i] = 0;
				}
				k--;
			}
			if(k==1) {
				digits = new int[len+1];
				digits[0] = 1;
			}
			return digits;
		}
    }
	
}