从n个字符中，找出m个排列组合

#include <string.h>
#include <stdio.h>
#include <stdlib.h>

void combine(char *value,char *result,int m)
{
    if(m == )
    {
        while(*value != '\0')
        {
            printf("%s%c\n",result,*value);
            value++;
        }
    }

    int value_len = strlen(value);
    int result_len =  strlen(result);

    int i = ;
    for(i = ;i < value_len - m + ;i++)
    {
        result[result_len] = *value;
        result[result_len + ] = '\0';
        value++;
        combine(value,result,m - );
    }
}

int main()
{
    printf("输入字符集：\n");
    char value[];
    scanf("%s",value);
    printf("输入组合的数字：\n");
    int m;
    scanf("%d",&m);

    char *result = (char *)malloc(m + );
    memset(result,,m + );

    combine(value,result,m);

    return ;
}