46. Permutations

Given a collection of distinct 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],
[3,2,1]
]

class Solution {
public:
vector<vector<int> > permute(vector<int>& nums) {
dfs(nums, 0);
return res;
}
private:
void dfs(vector<int>&nums, int cur){
if (cur == nums.size()){
res.push_back(nums);
}
for (int i = cur; i < nums.size(); i++){
swap(nums[cur], nums[i]);
dfs(nums, cur + 1);//注意这里是cur+1
swap(nums[cur], nums[i]);
}
}
vector<vector<int> > res;
};