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Permutations.cpp
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Permutations.cpp
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/*
Author: physician
Date: Feb 09, 2014
Update: Feb 09, 2014
Problem: Permutations
Difficulty: Easy
Source: http://oj.leetcode.com/problems/permutations/
Problem Description:
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].
Notes:
1. First implementation, recursion. DFS. Time O(n!), space O(n).
2. Compile using g++: g++ Permutations.cpp -o Permutations.
*/
# include <iostream>
# include <vector>
# include <algorithm>
using namespace std;
class Solution {
public:
vector<vector<int> > permute(vector<int> &num) {
sort(num.begin(), num.end());
vector<vector<int> > result;
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 (int i = 0; i < num.size(); ++i) {
if (find(path.begin(), path.end(), num[i]) == path.end()) {
path.push_back(num[i]);
dfs(num, path, result);
path.pop_back();
}
}
}
};
int main() {
int input[] = {1,2,3};
vector<int> num(input, input + sizeof(input) / sizeof(int));
Solution sol;
vector<vector<int> > solVec = sol.permute(num);
for (int i = 0; i < solVec.size(); ++i) {
cout << "[ ";
for (int j = 0; j < solVec[i].size(); ++j)
cout << solVec[i][j] << " ";
cout << "]" << endl;
}
}