[Leetcode] Permutations

最新推荐文章于 2019-05-10 11:15:43 发布

原创最新推荐文章于 2019-05-10 11:15:43 发布 · 379 阅读

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#DFS #dfs

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本文介绍了一种使用深度优先搜索(DFS)策略生成整数数组所有可能排列的方法。通过递归交换数组元素的位置来穷举所有可能性，最终得到全部的排列组合。

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].

Reference: http://exceptional-code.blogspot.com/2012/09/generating-all-permutations.html

http://blog.youkuaiyun.com/custqi/article/details/6455686

    class Solution {
    public:
        vector<vector<int> > permute(vector<int> &num) {
            // Start typing your C/C++ solution below
            // DO NOT write int main() function
           vector<vector<int> > result;
           dfs(result,num,0);
           return result;            
        }
        
        void dfs(vector<vector<int> > &result, vector<int> &num, int depth)
        {
           if(depth==num.size())
           {
               result.push_back(num);
           }
           
           for(int i=depth;i<num.size();i++)
           {
               swap(num[i],num[depth]);//DFS is implemented in another way here.
               dfs(result,num,depth+1);
               swap(num[i],num[depth]);               
           }
        }
    };