leetcode---Combinations

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],

]

class Solution {
public:
vector<vector<int>> ans;
vector<int> tmp;

void dfs(int dep, int maxDep, int n, int start)
{
if(dep == maxDep)
{
ans.push_back(tmp);
return;
}
for(int i=start; i<=n; i++)
{
tmp[dep] = i;
dfs(dep+1, maxDep, n, i+1);
}
}

vector<vector<int>> combine(int n, int k)
{
tmp.resize(k);
dfs(0, k, n, 1);
return ans;
}
};