407. Plus One【LintCode java】

Description

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.

Example

Given [1,2,3] which represents 123, return [1,2,4].

Given [9,9,9] which represents 999, return [1,0,0,0].

解题：此题注意进位即可，具体注意点标注在代码中，代码如下：

public class Solution {
    /**
     * @param digits: a number represented as an array of digits
     * @return: the result
     */
    public int[] plusOne(int[] digits) {
        // write your code here
        boolean[]carry = new boolean[digits.length];//默认false
        int n = digits.length;
        if(digits[n - 1] !=9){
            //无需进位
            digits[n - 1]++;
            return digits;
        }else{
            //有进位
            for(int i = n-1; i >= 0; i--){
                if(digits[i] == 9){
                    carry[i]=true;
                }else{
                    //很重要
                    break;
                }
            }
            if(carry[0] == true){
                int[]res = new int[n+1];
                res[0] = 1;
                return res;
            }else{
                int[]res = new int[n];
                for(int i = n - 1; i >= 0; i--){
                    if(carry[i] == true){
                        res[i] = 0;
                    }else if(carry[i] == false && carry[i+1] == true){
                        res[i] = digits[i] + 1;
                    }else{
                        res[i] = digits[i];
                    }
                }
                return res;
            }
        }
    }
}