[LeetCode] 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]

.

class Solution {
public:
vector<vector<int> > permute(vector<int> &num) {
vector<int> te;
vector<vector<int> >res,temp;//temp里存放中间值
int len = num.size();
if(len<=0)
return res;
for(int i=0;i<len;i++)
{
te.push_back(num[i]);
temp.push_back(te);
te.clear();
}//end for

while(!temp.empty())
{
te = temp.back();
temp.pop_back();
if(te.size()==len)
{
res.push_back(te);
continue;
}
for(int i=0;i<len;i++)
{
if(find(te.begin(),te.end(),num[i])==te.end())
{
te.push_back(num[i]);
temp.push_back(te);
te.pop_back();
}

}

}//end while
return res;

}
};

依然是以前堆栈的思想，但用vector实现也不错。