程序代码：

#include "stdio.h"
#include "string.h"

char f_p[] = {"%.0s"};
char s[8];

void f (char* num, int len, int len_r, int c, int c_r, int* c_s)
{
    int i;

    for (i=0; i<len-(c-1) && c>0; i++)
    {        
        f_p[2] = 1 + 0x30;
        printf (f_p, &num[i]);
        (*c_s)++;
        strncat (s, &num[i], 1);
        
        if (*c_s == c_r)
        {
            printf ("\n");
            (*c_s) = 0;

            if ((s[c_r-1] == (len_r+0x30)) && (c_r>1))
            {
                int i;
                for (i=c_r-1; i>0; i--)
                {
                    if (s[i-1]+1 == s[i])
                    {
                        continue;
                    }
                    else
                    {
                        break;
                    }
                }
                
                if (i==0)
                {
                    s[0] = 0;
                    return;
                }
                else
                {
                    int count;
                    s[i-1] = 0;
                    
                    count = (c_r-1) - i + 1;        
                    f_p[2] = c_r - (count + 1) + 0x30;
                    printf (f_p, s);
                    (*c_s) = c_r - (count+1);
                }
            }
            else        
            {
                s[c_r-1] = 0;

                f_p[2] = c_r-1 + 0x30;
                printf (f_p, s);
                (*c_s) = c_r-1;
            }
        }
        
        f (&num[i+1], len-1-i, len_r, c-1, c_r, c_s);
    }
}

 
int main (int argc, char** argv)
{
    char f_num[] = {"1234"};
    int len;
    int c_s;
    int i;

    c_s = 0;
    len = strlen (f_num);

    for (i=0; i<len; i++)
    {
        f (f_num, len, len, i, i, &c_s);
    }

    return 0;
}

程序代码：

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

void sub_show_comb(char * set, int n, char * stack, int count, int index)
{
    int i;
    if(index == count)
    {
        puts(stack);
        return;
    }
    for(i = 0; i <= n - count + index; i++)
    {
        stack[index] = set[i];
        sub_show_comb(set + i + 1, n - i - 1, stack, count, index + 1);
    }
}

void show_comb(char * set)
{
    char * stack;
    int n, i;
    n = strlen(set);
    stack = (char *)malloc(n + 1);
    for(i = 1; i <= n; i++)
    {
        stack[i] = '\0';
        sub_show_comb(set, n, stack, i, 0);
    }
    free(stack);
}

int main()
{
    char s[] = "1234";
    show_comb(s);
    return 0;
}

程序代码：

#include <stdio.h>
void comb(char *s,char *d,int l,int p)
{
    int i,j;
    char a[10];
    for(i=0;d[i];i++)a[i]=d[i];
    a[i]=0;
    if(i==l)
        printf("%s,",a);
    else
    {
        for(j=p;s[j];j++)
        {
            a[i]=s[j];
            a[i+1]=0;
            comb(s,a,l,j+1);
        }
    }
}
void main()
{
    char a[10],b[]="1234";
    int i;
    a[0]=0;
    for(i=0;b[i];i++)comb(b,a,i+1,0);
    printf("\n");
}