Combinations <leetcode>

Given two integersNAndK, Return all possible combinationsKNumbers out of 1...N.

For example,
IfN= 4 andK= 2, a solution is:

[[2, 4], [3, 4], [2, 3], [1, 2], [1, 3], [1, 4],]

Algorithm: This question is very simple, but I didn't expect it at the time. I suddenly realized it was just a query on the Internet, that is, to construct a solution space, and then solve it with backtracing. soeasy, I don't want to talk about it anymore. Go to the Code:

 1 class Solution { 2 public: 3     vector<vector<int>>  result; 4     vector<int>  node; 5     vector<vector<int> > combine(int n, int k) { 6          result.clear(); 7          node.resize(k); 8          doit(0,n,k,1); 9          return result;10     }11     void doit(int dep,int n,int k,int start)12     {13         if(dep==k)14         {15             result.push_back(node);16             return;17         }18         else19         {20             for(int i=start;i<=n-k+1+dep;i++)21             {22                 node[dep]=i;23                 doit(dep+1,n,k,i+1);24             }25         }26     }27 };

 

Combinations <leetcode>