HDU - 2181 dfs [kuangbin带你飞]专题二

#include<cstdio>
#include<vector>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn = 25;
int vis[maxn];
vector<int>v[25];

int ans[maxn], num, m;

void print() {
printf("%d: ", num);
for(int i = 0; i < 20; ++i) printf(" %d", ans[i]);
printf(" %d\n", m);
}
void dfs(int u, int cnt) {
ans[cnt] = u;
if(cnt == 19) {
int flag = 0;
for(int i = 0; i < 3; ++i){
if(v[u][i] == m) flag = 1;
}
if(flag) {
num++;
print();
}
return;
}
if(cnt >= 20) return;
vis[u] = 1;
for(int i = 0; i < 3; ++i) {
if(vis[v[u][i]]) continue;
dfs(v[u][i], cnt + 1);
}
vis[u] = 0;
}

int main(){
int a[3];

for(int i = 1; i <= 20; ++i) {
v[i].clear();
for(int j = 0; j < 3; ++j){
scanf("%d", &a[j]);
v[i].push_back(a[j]);
}
sort(v[i].begin(), v[i].end()); //确保字典序最小
}

while(scanf("%d", &m) == 1 && m) {
memset(vis, 0, sizeof(vis));
num = 0;
dfs(m, 0);
}

return 0;
}