递归算法---字符串---全/部分组合和全排列

#include <stdio.h>
#include <string.h>
void combine(char *src, char *out,int rec, int start, int end)
{
        int i;
        if(start==end)
                return;
        for(i=start;i<end;i++){
                out[rec]=src[i];
                out[rec+1]='\0';
                printf("%s\n",out);
                combine(src,out,rec+1,i+1,end);
        }       
}       
int main(int argc, char *argv[])
{
        int len=strlen(argv[1]);
        char out[len];
        combine(argv[1],out,0,0,len);
        return 0;
}

/**
  *从字符串中取出n个的组合
  */
#include <stdio.h>
#include <string.h>
void combine(char *src,char *out,int start,int rec,int end, int n)
{

        int i;
        if(n>end)
                n=end;
        for(i=start;i<end;i++){
                out[rec]=src[i];
                if(n==1){
                        out[rec+1]='\0';
                        printf("%s\n",out);
                }else {
                        combine(src,out,i+1,rec+1,end,n-1);
                }
        }
}
int main(int argc, char *argv[])
{
        char out[strlen(argv[1])];
        combine(argv[1],out,0,0,strlen(argv[1]),atoi(argv[2]));
        return 0;
}

#include <stdio.h>
#include <string.h>
void arrange(char *src,int start,int end)
{
        int i;
        char tmp;
        if(start==end){
                printf("%s\n",src);
        }
        for(i=start;i<end;i++){
                tmp=src[start];src[start]=src[i];src[i]=tmp;
                arrange(src,start+1,end);
                tmp=src[start];src[start]=src[i];src[i]=tmp;
        }
}
int main(int argc, char *argv[])
{
        arrange(argv[1],0,strlen(argv[1]));
        return 0;
}