Permutations

Given a collection of numbers, return all possible permutations.

For example,
[1,2,3] have the following permutations:
[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].

简单递归题，同样没查最佳算法，今天还没看书呢……

class Solution {
public:
    vector<vector<int> > re;
    vector<vector<int> > permute(vector<int> &num) {
        vector<int> no;
        vector<int> count;
        sort(num.begin(),num.end());
        if(num.size()==0)
        return re;

        no.push_back(num[0]);
        count.push_back(1);
        int j = 0;
        for(int i = 1 ; i < num.size();i++)
        {
            if(num[i] == num[i-1])count[j]++;
            else
            {
                no.push_back(num[i]);
                j++;
                count.push_back(1);
            }
        }
        vector<int>temp;
        per(no,count,num.size(),temp,-1);
        
    return re;
    }
    void per(vector<int> no , vector<int> count, int left,vector<int>now,int should)
    {

        int i=0;
        if(should != -1){
            now.push_back(no[should]);
            count[should]--;
            
        }
        if(left == 0)
        {
            re.push_back(now);
            return;
        }

        for(i=0;i<no.size();i++)
        {
            if(count[i]>0)
            {
                per(no,count,left-1,now,i);
            }
        }
    }
};