class Solution {
public:
std::vector<vector<int>> res;
std::vector<int> path;
void backtracking(int n, int k, int startidx){
if (path.size()==k){
res.push_back(path);
return;
}
for (int i = startidx; i <= n; i++){
path.push_back(i);
backtracking(n, k, i+1);
// 注意pop.back()空括号 错误path.pop_back(i)
path.pop_back();
}
}
std::vector<vector<int>> combine(int n, int k) {
backtracking(n, k, 1);
return res;
}
};
class Solution {
public:
std::vector<vector<int>> res;
std::vector<int> path;
void backtracking(int n, int k, int startidx){
if (path.size()==k){
res.push_back(path);
return;
}
// i <= 剪枝
for (int i = startidx; i <= n-(k-path.size())+1; i++){
path.push_back(i);
backtracking(n, k, i+1);
// 注意pop.back()空括号 错误path.pop_back(i)
path.pop_back();
}
}
std::vector<vector<int>> combine(int n, int k) {
backtracking(n, k, 1);
return res;
}
};