Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.
For example,
If n = 4 and k = 2, a
solution is:
[ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4], ]
不知道有没有更好的方法。
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class
Solution {public: vector<vector<int> > re; vector<vector<int> > combine(int
n, int
k) { vector<int> m; if(n < k)return
re; cal(n,0,k,m); return
re; } void
cal(int
n, int
begin,int
num,vector<int> already) { if(begin != 0) already.push_back(begin); if(num == 0){ re.push_back(already); return; } for(int
i = begin + 1 ;i <= n - num+1 ;i++) { cal(n ,i , num-1,already); } }}; |
原文：http://www.cnblogs.com/pengyu2003/p/3599331.html