n个字符选出m个字符的组合 

 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 }

 

posted @ 2016-07-28 11:04  ranran1203  阅读(362)  评论(0)    收藏  举报