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Combination_base_case.cc
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Combination_base_case.cc
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#include<iostream>
#include<vector>
using namespace std;
class Solution {
public:
vector<vector<int> > combine(int n, int k) {
if (!n) return vector<vector<int>> ();
bool ref[n];
for (int i = 0; i < n; i++) ref[i] = false;
vector<vector<int>> ret;
_com(n, k, 0, vector<int>(), ret);
return ret;
}
void _com(int n, int k, int i, vector<int> pre, vector<vector<int>> &ret) {
if (!k) {
ret.push_back(pre);
return;
}
if (i == n) return;
_com(n, k, i + 1, pre, ret);
pre.push_back(i + 1);
_com(n, k - 1, i + 1, pre, ret);
}
//----------------------------------------------//
vector<vector<int> > combine(int n, int k) {
vector<vector<int> > ret;
if (n < 1 || k < 1)
return ret;
if (n < k)
return ret;
if (k == 1) {
vector<int> tmp;
tmp.push_back(n);
ret.push_back(tmp);
}
vector<vector<int> > ret_tmp = combine(n - 1, k - 1);
for (int i = 0; i < ret_tmp.size(); ++i) {
ret_tmp[i].push_back(n);
ret.push_back(ret_tmp[i]);
}
ret_tmp = combine(n - 1, k);
for (int i = 0; i < ret_tmp.size(); i++) {
ret.push_back(ret_tmp[i]);
}
return ret;
}
};
int main(int argc, char **argv) {
Solution sol;
vector<vector<int> > res = sol.combine(4, 2);
for (int i = 0; i < res.size(); ++i) {
vector<int> tmp = res[i];
for (int j = 0; j < tmp.size(); ++j) {
cout << tmp[j] << " ";
}
cout << endl;
}
return 1;
}