排列组合算法之排列算法 C++

void swap(char& a, char& b){
    char temp = a;
    a = b;
    b = temp;
}

void perm(vector<char>& vec, int start, int end, vector<vector<char>>& res){
    if(start == end){
        vector<char> re(end, 0);
        for(int i = 0; i < end; i++){
            re[i] = vec[i];
        }
        res.emplace_back(re);
        return;
    }
    for( int i = start; i < end; i++){
        swap(vec[start], vec[i]);
        perm(vec, start+1, end, res);
        swap(vec[i], vec[start]);
    }
}

int test_perm(){
    vector<char> vec = {'a', 'b', 'c', 'd', 'e'};
    vector<vector<char>> res;
    perm(vec, 0, (int)vec.size(), res);
    return 0;
}