[leetcode][66] Plus One

Posted 2021-01-04 ekoeko

66. Plus One

Given a non-empty array of digits representing a non-negative integer, plus one to the integer.

The digits are stored such that the most significant digit is at the head of the list, and each element in the array contain a single digit.

You may assume the integer does not contain any leading zero, except the number 0 itself.

Example 1:

Input: [1,2,3]
Output: [1,2,4]
Explanation: The array represents the integer 123.

Example 2:

Input: [4,3,2,1]
Output: [4,3,2,2]
Explanation: The array represents the integer 4321.

解析

很简单，就是把一个数组当成数字加一，考虑下进位就行了。

参考答案（自己写的）：

class Solution {
    public int[] plusOne(int[] digits) {
        int index = digits.length-1;
        if (digits[index] != 9) {
            digits[index] += 1;
            return digits;
        }
        digits[index] = 0;
        index--;
        while(index >= 0 && digits[index] == 9) {
            digits[index--] = 0;
        }
        if (index < 0) {
            int[] res = new int[digits.length + 1];
            res[0] = 1;
            return res;
        } else {
            digits[index] += 1;
            return digits;
        }
    }
}

当需要增加一位的时候需要new一个数组出来，把0位置上的数字置一就行了，其他位置默认就是0；