LeetCode - 46. Permutations

简介: 46. Permutations  Problem's Link  ---------------------------------------------------------------------------- Mean:  给定一个数组,求这个数组的全排列.

46. Permutations 

Problem's Link

 ----------------------------------------------------------------------------

Mean: 

给定一个数组,求这个数组的全排列.

analyse:

方法1:调用自带函数next_permutation(_BIter,_BIter)

方法2:自己手写一个permutation函数,很简单.

Time complexity: O(N)

 

view code

#include <bits/stdc++.h>
using namespace std;

// way 1: use system's function:next_permutation(iter* begin,iter* end);
//class Solution
//{
//public:
//    vector<vector<int>> permute(vector<int>& nums)
//    {
//        vector<vector<int>> res;
//        sort(nums.begin(),nums.end());
//        res.push_back(nums);
//        while(next_permutation(nums.begin(),nums.end()))
//            res.push_back(nums);
//        return res;
//    }
//};

class Solution
{
public :
    vector < vector < int >> permute( vector < int > nums)
    {
        vector < vector < int >> res;
        solvePermute( res , nums , 0);
        return res;
    }
   
    void solvePermute( vector < vector < int >>& res , vector < int > nums , int begin)
    {
        if( begin >= nums . size())
        {
            res . push_back( nums);
            return;
        }
        for( int i = begin; i < nums . size(); ++ i)
        {
            swap( nums [ i ], nums [ begin ]);
            solvePermute( res , nums , begin + 1);
            swap( nums [ i ], nums [ begin ]);
        }
    }
};

int main()
{
    int n;
    while( cin >>n)
    {
        vector < int > ve(n);
        for( int i = 0; i <n; ++ i)
            cin >> ve [ i ];
        Solution solution;
        vector < vector < int >> ans = solution . permute( ve);
        for( auto p1: ans)
        {
            for( auto p2: p1)
            {
                cout << p2 << " ";
            }
            cout << endl;
        }
    }
    return 0;
}
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