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#include <stdio.h>
#include <stdlib.h>
#define COMBINE_M 2
void swap(char* a, char* b)
{
char tmp = *a;
*a = *b;
*b = tmp;
}
void combine(char A[], int n, int m, int b[])
{
int i;
int j;
for(i=n;i>=m;i--)
{
b[m-1] = i-1;
if(m>1)
combine( A, i-1, m-1, b);
else
{
for(j=0;j<COMBINE_M;j++)
printf("%c\t",A[b[j]]);
printf("\n");
}
}
}
void permute(char A[], int m, int n)
{
int i;
if(m == n)
{
for(i=0;i<m;i++)
printf("%c",A[i]);
printf("\n");
}
else
{
for(i=m;i<n;i++)
{
swap(A+i,A+m);
permute(A,m+1,n);
swap(A+i,A+m);
}
}
}
int main(int argc, char *argv[])
{
char A[] = "abcd";
int* B = (int*)malloc(strlen(A)*sizeof(int) + 1 );
printf("combile is:\n");
combine(A, 4, COMBINE_M, B);
printf("permute is:\n");
permute(A,0,3);
system("PAUSE");
return 0;
}
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