leetcode第一刷_Permutations

產生全排列的經典問題，遞迴方法的典範。

bool visited[10000];void getPermutation(vector<int> &num, vector<vector<int> > &res, vector<int> &pres, int len, int p){    if(p == len){        res.push_back(pres);        return;    }    for(int i=0;i<len;i++){        if(!visited[i]){            visited[i] = 1;            pres[p] = num[i];            getPermutation(num, res, pres, len, p+1);            visited[i] = 0;        }    }}class Solution {public:    vector<vector<int> > permute(vector<int> &num) {        int msize = num.size();        vector<vector<int> > res;        vector<int> pres(msize);        if(msize == 0)            return res;        memset(visited, 0, sizeof(visited));        getPermutation(num, res, pres, msize, 0);        return res;    }};