排列數
#include <iostream>
#include <vector>
using namespace std;
int n;
int* a = new int[n];
vector<int> path;
void dfs(int step, int state) {
if (step == n) {
for (auto x : path) cout << x << " ";
cout << endl;
}
else {
for (int i = 0; i < n; i++) {
if (!(state >> i & 1)) {
path.push_back(i + 1);
dfs(step + 1, state | (1 << i));
path.pop_back();
}
}
}
}
int main() {
cin >> n;
for (int i = 1; i <= n; i++) {
a[i - 1] = i;
}
dfs(0, 0);
delete[] a;
return 0;
}
組合數
#include <iostream>
using namespace std;
int n, m;
int* a = new int[n];
void dfs(int step, int sum, int state) {
if (sum + n - step < m) return;
if (sum == m) {
for (int i = 0; i < n; i++) {
if (state >> i & 1) {
cout << a[i] << " ";
}
}
cout << endl;
return;
}
dfs(step + 1, sum + 1, state | 1 << step);
dfs(step + 1, sum, state);
}
int main() {
cin >> n >> m;
for (int i = 0; i < n; i++) {
cin >> a[i];
}
dfs(0, 0, 0);
delete[] a;
return 0;
}