77. Combinations
题目
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],
]
解析
class Solution_77 {
public:
void help(vector<vector<int>>& vecs, vector<int> &vec,int i,int k,int n )
{
if (k==0)
{
vecs.push_back(vec);
return;
}
if (i>n)
{
return;
}
vec.push_back(i + 1);
help(vecs, vec, i + 1, k-1, n);
vec.pop_back();
help(vecs, vec, i + 1, k, n);
return;
}
vector<vector<int>> combine(int n, int k) {
vector<vector<int>> vecs;
vector<int> vec;
help(vecs,vec,0,k,n);
return vecs;
}
};
题目来源
