【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<vector<int> > result;
sort(num.begin(), num.end());
vector<int> path;
dfs(num, path, result);
return result;
}
private:
void dfs(vector<int> &num, vector<int> &path, vector<vector<int>> &result) {
if (path.size() == num.size()) {
result.push_back(path);
return;
}
for (auto i : num) {
if (find(path.begin(), path.end(), i) == path.end()) {
path.push_back(i);
dfs(num, path, result);
path.pop_back();
}
}
}
};

View Code
可以利用next permutation的方法，一个一个求，也可以用dfs的方法来求所有的排列。上面的代码是dfs版。