77. 组合 - 力扣（LeetCode）
class Solution {private:
vector<vector<int>> result;
vector<int> path;
void backtracking(int n, int k, int startIndex) {
if (path.size() == k) {
result.push_back(path);
return;
}
for (int i = startIndex; i <= n - (k - path.size()) + 1; i++) { // 优化的地方
path.push_back(i); // 处理节点
backtracking(n, k, i + 1);
path.pop_back(); // 回溯，撤销处理的节点
}
}
public:
vector<vector<int>> combine(int n, int k) {
backtracking(n, k, 1);
return result;
}
}; #include<iostream>
#include<bits/stdc++.h>
using namespace std;
vector<int>path;
vector<vector<int>>result;
void backtracking(int n,int k,int startindex)
{
if(path.size()==k)
{
result.push_back(path);
return ;
}
for(int i=startindex;i<=n;i++)
{
path.push_back(i);
backtracking(n,k,i+1);
path.pop_back();
}
}
int main()
{
int n,k;
cin>>n>>k;
backtracking(n,k,1);
for (const auto& comb : result)
{
for (int num : comb)
{
cout << num << " ";
}
cout << endl;
}
return 0;
}
剪枝操作:
#include<iostream>
#include<bits/stdc++.h>
using namespace std;
vector<int>path;
vector<vector<int>>result;
void backtracking(int n,int k,int startindex)
{
if(path.size()==k)
{
result.push_back(path);
return ;
}
for(int i=startindex;i<=n-(k-path.size())+1;i++)
{
path.push_back(i);
backtracking(n,k,i+1);
path.pop_back();
}
}
int main()
{
int n,k;
cin>>n>>k;
backtracking(n,k,1);
for (const auto& comb : result)
{
for (int num : comb)
{
cout << num << " ";
}
cout << endl;
}
return 0;
} 输出二维数组
for (auto& j : result)
{
for (int i : j)
{
cout << i << " ";
}
cout << endl;
}
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