leetcode第一刷_Permutations

生成全排列的经典问题。递归方法的典范。

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;
    }
};