我想用char数组解决输出时三位数之前的“0”，于是用了很多的循环，我自己改了几次，但2，3，4测试点就是无法通过，很苦恼。请问一下代码还有什么地方欠考虑。

#include<iostream>
#include<string>
#include<algorithm>
using namespace std;

bool cmp(char a, char b)
{
    return a > b;
}
int main()
{
    char number1[4], number2[4];
    int n = 0;
    for (int i = 0; i < 4; i++)
    {
        cin>>number1[i];
    }
    if (number1[0] == number1[1]&& number1[1]== number1[2]&& number1[2]== number1[3])//4位数字相同时的输出
    {
        for (int i = 0; i < 4; i++)
        {
            cout << number1[i];
        }
        printf(" - ");
        for (int i = 0; i < 4; i++)
        {
            cout << number1[i];
        }
        printf(" = 0000");
    }
    else//其他情况
    {

        while (n != 6174)
        {
            for (int i = 0; i < 4; i++)
            {
                number2[i] = number1[i];
            }
            sort(number1, number1 + 4, cmp);//较大的数
            sort(number2, number2 + 4);//较小的数
            for (int i = 0; i < 4; i++)//输出相减的两个数
            {
                cout << number1[i];
            }
            printf(" - ");
            for (int i = 0; i < 4; i++)
            {
                cout << number2[i];
            }



            int n1 = 0, n2 = 0,t=1;
            for (int i = 3; i >=0; i--)//输出相减结果
            {
                n1 += ((int)number1[i]-48) * t;
                t *= 10;
            }
            t = 1;
            for (int i = 3; i >= 0; i--)
            {
                n2 += ((int)number2[i]-48) * t;
                t *= 10;
            }
            n = n1 - n2;
            printf(" = %04d\n", n);

            int temp = n;
            int i = 0;
            while(i<4)//记录相减的结果
            {
                number1[i++] = (char)(temp % 10+48);
                temp /= 10;
            }
        }

    }
    return 0;
}

我搜索到了题目，你注意看

输入格式：
输入给出一个(0, 10000)区间内的正整数N。

你没有考虑<10000的情况

如果是 < 10000，你的程序还在等待输入，而实际上应该是补0

我把输入修改了下，你看看行不行

// Q1055005.cpp : Defines the entry point for the console application.
//

#include<iostream>
#include<string>
#include<algorithm>
using namespace std;

bool cmp(char a, char b)
{
    return a > b;
}
int main()
{
    char number1[4], number2[4];
    int n = 0;
    int input;
    cin >> input;
    for (int i = 0; i < 4; i++)
    {
        number1[4-i-1] = input % 10 + '0';
        input /= 10;
    }
    if (number1[0] == number1[1]&& number1[1]== number1[2]&& number1[2]== number1[3])//4位数字相同时的输出
    {
        for (int i = 0; i < 4; i++)
        {
            cout << number1[i];
        }
        printf(" - ");
        for (int i = 0; i < 4; i++)
        {
            cout << number1[i];
        }
        printf(" = 0000");
    }
    else//其他情况
    {

        while (n != 6174)
        {
            for (int i = 0; i < 4; i++)
            {
                number2[i] = number1[i];
            }
            sort(number1, number1 + 4, cmp);//较大的数
            sort(number2, number2 + 4);//较小的数
            for (int i = 0; i < 4; i++)//输出相减的两个数
            {
                cout << number1[i];
            }
            printf(" - ");
            for (int i = 0; i < 4; i++)
            {
                cout << number2[i];
            }



            int n1 = 0, n2 = 0,t=1;
            for (int i = 3; i >=0; i--)//输出相减结果
            {
                n1 += ((int)number1[i]-48) * t;
                t *= 10;
            }
            t = 1;
            for (int i = 3; i >= 0; i--)
            {
                n2 += ((int)number2[i]-48) * t;
                t *= 10;
            }
            n = n1 - n2;
            printf(" = %04d\n", n);

            int temp = n;
            int i = 0;
            while(i<4)//记录相减的结果
            {
                number1[i++] = (char)(temp % 10+48);
                temp /= 10;
            }
        }

    }
    return 0;
}

问题解决的话，请点下采纳，谢谢合作