LeetCode Permutations

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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].

思路：一个用stl，一个就是dfs，每次固定前cur个，然后依次和之后的数交换

class Solution {
public:
    vector<vector<int> > permute(vector<int> &num) {
        sort(num.begin(), num.end());
        vector<vector<int> > ans;
        do {
            ans.push_back(num);
        } while (next_permutation(num.begin(), num.end()));
        return ans;
    }
};

class Solution {
public:
    void dfs(vector<int> &num, vector<vector<int> > &ans, int cur, int n) {
        if (cur == n) {
            ans.push_back(num);
        }

        for (int i = cur; i < n; i++) {
            swap(num[cur], num[i]);
            dfs(num, ans, cur+1, n);
            swap(num[cur], num[i]);
        }
    }

    vector<vector<int> > permute(vector<int> &num) {
        vector<vector<int> > ans; 
        int n = num.size();
        dfs(num, ans, 0, n);
        return ans;
    }
};

LeetCode Permutations

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原文地址：http://blog.csdn.net/u011345136/article/details/44116095