一个字符串的组合数, 如abc, 输出的是a, b, c, ac, ab, bc, abc, 即包含顺序的组合.

类似位(bit)的全排列, 如 001, 010, 100, 011, 101, 110, 111.

代码:

/*
* main.cpp
*
* Created on: 2014.7.20
* Author: Spike
*/

/*eclipse cdt, gcc 4.8.1*/

#include
#include
#include
#include

using namespace std;

string BinaryString(string s, int i) {
string tmp;
int k=0;
while (i != 0) {
if (i & 0x1)
tmp.push_back(s[k]);
k++;
i >>= 1;
}
return tmp;
}

vector Combination(string s) {
vector vs;
if (s.length() == 0)
return vs;
int num = pow(2.0, s.length());
for (int i=1; i string tmp = BinaryString(s, i);
vs.push_back(tmp);
}
return vs;
}

int main(void)
{
string s = "abc";
vector vs = Combination(s);
for (size_t i=0; i cout << vs[i] << endl;
}
return 0;
}

输出:

a
b
ab
c
ac
bc
abc