1 #include<iostream>
2 #include<vector>
3 #include<string>
4 using namespace std;
5 void combine(char *str, int begin, int m, vector<char>&vec)
6 {
7 if (m == 0)//当m为0时，表明字符数已经选够
8 {
9 vector<char>::iterator it = vec.begin();
10 for (; it != vec.end(); it++)
11 cout << *it;
12 cout << endl;
13 return;
14 }
15 if (begin == strlen(str))//开始位置到达字符串 末尾时返回
16 return;
17 vec.push_back(str[begin]);//情况1是从剩余的字符中选择m-1个
18 combine(str, begin + 1, m - 1, vec);
19 vec.pop_back();
20 combine(str, begin + 1, m, vec);//从全部的剩余字符中再选出m个
21 }
22 void combination(char *str, int m)
23 {
24 if (str==NULL || m <= 0 || m > strlen(str))
25 return;
26 vector<char> vec;
27
28 combine(str, 0, m, vec);
29
30 }
31
32 int main()
33 {
34 char *str = "abcd";
35 combination(str, 3);
36 cin.get();
37 return 0;
38 }
