code第一部分数组：第十六题  数组表示数，加一操作

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

#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include <vector>
using namespace std;

int * addone(int *a,int n)
{

    int *ans;
    for (int i = n-1; i >=0; i--)
    {
        if (a[i]!=9)
        {
            a[i]++;
            break;
        }
        else
        {
            a[i]=0;
        }
    }

    if (a[0]==0)
    {
        ans=(int *)malloc(sizeof(int)*(n+1));
        for (int i = n; i >0; i--)
        {
            ans[i]=a[i-1];
        }
        ans[0]=1;
        return ans;
    }
    else
    {
        return a;
    }
}

vector<int> plusOne(vector<int> &digits) {
    int i;
    for(i = digits.size() - 1;i >= 0;--i){
        if(digits[i] != 9){
            digits[i]++;
            break;
        }
        else {
            digits[i] = 0;
        }
    }
    if(digits[0]==0) {
        digits.insert(digits.begin(),1);
    }

    return digits;
}

int main()
{
    int a[4]={9,9,9,9};
    int len=0;

    if (a[3]==9)
    {
        len=sizeof(a)/sizeof(int)+1;
    }
    else
    {
        len=sizeof(a)/sizeof(int);
    }

    int *b = addone(a,4);

    for (int i = 0; i < len; i++)
    {
        cout<<b[i];
    }

    cout<<endl;

    vector<int> result;
    vector<int> array = {1,9,9};
    result = plusOne(array);
    int n = result.size();
    for(int i = 0;i < n;i++){
        cout<<result[i];
    }

    return 0;
}