[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> > ans;
vector<int> v;
bool *nums;
int len;
vector<vector<int> > permute(vector<int> &num) {
len = num.size();
nums = new bool[len];
for(int i = 0;i < len;i ++)
nums[i] = true;
dfs(num);
return ans;
}
void dfs(vector<int> &num){
if(v.size() == len){
ans.push_back(v);
return;
}
for(int i = 0;i < len;i ++){
if(nums[i]){
v.push_back(num[i]);
nums[i] = false;
dfs(num);
nums[i] = true;
v.pop_back();
}
}
}
};