OJ-尼科彻斯定理

#include <stdio.h>
#include <string.h>
#define N 1000

int data2str(int num,char* str)
{
    char* tmp = str;
    int len = 0;
    int data;
    int i,j;
    int mid;

    while (num>0)
    {
        data = num%10;
        tmp[len++] = '0'+data;
        num = num/10;
    }
    j = len-1;
    for (i=0;i<len/2;i++,j--)
    {
        mid = tmp[i];
        tmp[i] = tmp[j];
        tmp[j] = mid;
    }
    return len;
}

int Machst(int data)
{
    int MAX = data*data*data;
    int sum = 0;
    int i;
    char str[N]={0};
    char num[10]={0};
    int len_data=0;
    int len = 0;

    if (data<1 || data>100)
    {
        return -1;
    }

    for (i=data*data-data+1;i<=MAX; i+=2)
    {
        sum += i;
        len_data = data2str(i,num);
        strncpy(str+len,num,len_data);
        len +=len_data;

        if (sum == MAX)
        {
            str[len]='\0';
            printf("%s\n",str);
            return 0;
        }
        else if (sum > MAX)
        {
            return -1;
        }
        strncpy(str+len,"+",1);
        len += 1;
    }
    return -1;
}

int main()
{
    int data;

    scanf("%d",&data);
    if (Machst(data) == -1)
    {
        printf("-1\n");
    }
    return 0;
}