///Permutation///#include 
    
     #include 
     
      void Swap(char* p1, char* p2) {	char temp = *p1;	*p1 = *p2;	*p2 = temp;}void Permutation_bad(char* pStr, char* pStart);void Permutation(char* pStr) {	if(pStr == NULL)		return;	Permutation_bad(pStr, pStr);}void Permutation_bad(char* pStr, char* pStart) {	if(*pStart == '\0') {		printf("%s.\n", pStr);		return;	}	char* pIndex = pStart;	while(*pIndex != '\0') {		Swap(pStart, pIndex);		Permutation_bad(pStr, pStart+1);		Swap(pStart, pIndex);		++pIndex;	}}// ====================测试代码====================void Test(char* pStr){    if(pStr == NULL)        printf("Test for NULL begins:\n");    else        printf("Test for %s begins:\n", pStr);    Permutation(pStr);    printf("\n");}int main(int argc, char* argv[]){    Test(NULL);    char string1[] = "";    Test(string1);    char string2[] = "a";    Test(string2);    char string3[] = "ab";    Test(string3);    char string4[] = "abcd";    Test(string4);    return 0;}
     
    

Combination///#include 
    
     #include 
     
      #include 
      
       #include 
       
        void Combination_m(char* pStr, int m, std::vector
        
         & result);void Combination(char* pStr) {	if(pStr == NULL || pStr == '\0')		return;	int number = strlen(pStr);	for(int i=1; i<=number; ++i) {		std::vector
         
           result; Combination_m(pStr, i, result); }}void Combination_m(char* pStr, int m, std::vector
          
           & result) { if(pStr == NULL || (*pStr == '\0' && m != 0)) return; if(m == 0) { for(std::vector
           
            ::iterator iter = result.begin(); iter