递归实现排列
留着明早省赛之前看
#include<iostream>
using namespace std;
int arr[10010];
int brr[10010];
int n,k;
void dfs(int num){
if(num > n){
for(int i = 1;i <= n;i++){
cout << arr[i] << " ";
}
cout << endl;
return;
}
for(int i = 1;i <= n;i++){
if(brr[i] == 0){
brr[i] = 1;
arr[num] = i;
dfs(num + 1);
brr[i] = 0;
arr[num]= 0;
}
}
}
int main()
{
cin >> n >> k;
dfs(1);
return 0;
}
递归实现组合型枚举
#include<iostream>
using namespace std;
int arr[10010];
int brr[10010];
int n, k;
void dfs(int num,int start) {
if(num - 1 + n - start + 1 < k){
return;
}
if (num > k) {
for (int i = 1; i <= k; i++) {
cout << arr[i] << " ";
}
cout << endl;
return;
}
for (int i = start; i <= n; i++) {
arr[num] = i;
dfs(num + 1, i + 1);
arr[num] = 0;
}
}
int main()
{
cin >> n >> k;
dfs(1,1);
return 0;
}
递归实现指数
#include<iostream>
using namespace std;
int n;
int* arr = new int[10000] {0};
int main()
{
void dfs(int);
cin >> n;
dfs(1);
}
void dfs(int x) {
if (x > n) {
for (int i = 1; i <= n; i++) {
if (arr[i] == 1) {
cout << i << " ";
}
}
cout << endl;
return;
}
arr[x] = 2;
dfs(x + 1);
arr[x] = 0;
arr[x] = 1;
dfs(x + 1);
arr[x] = 0;
}