UVA208 Firetruck 消防车（并查集，dfs）

#include<bits/stdc++.h>
using namespace std;
const int maxn = 21;

int p[maxn],cnt[maxn];
void init(int n) {
for(int i = 1;i <= n; i++) p[i] = i,cnt[i] = 1;
}
int Find(int x) { return p[x] == x ? x : p[x] = Find(p[x]); }

bool G0[maxn][maxn];
int G[maxn][maxn],deg[maxn];

int maxd;
int path[maxn];
bool vis[maxn];
int k,Count;
void dfs(int d,int cur)
{
if(cur == k){
printf("1");
for(int i = 1; i < d; i++)
printf(" %d",path[i]);
puts("");
Count++;
return;
}
if(d == maxd) return;
for(int i = 0; i < deg[cur]; i++){
int v = G[cur][i];
if(vis[v]) continue;
vis[v] = 1;
path[d] = v;
dfs(d+1,v);
vis[v] = 0;
}
}

int main()
{
//freopen("in.txt","r",stdin);
int cas = 0;
while(~scanf("%d",&k)){
printf("CASE %d:\n",++cas);
int u,v,n = 0;
init(20);
memset(G0,0,sizeof(G0));
memset(deg,0,sizeof(deg));
while(scanf("%d%d",&u,&v),u){
G0[u][v] = G0[v][u] = 1;
n = max(n,v);
n = max(n,u);
int s1 = Find(u), s2 = Find(v);
if(s1 != s2) {p[s1] = s2; cnt[s2] += cnt[s1];}
}
if(Find(k) != Find(1)) {printf("There are 0 routes from the firestation to streetcorner %d.\n",k); continue;}
for(int i = 1; i <= n; i++)
for(int j = 1; j <= n; j++) if(G0[i][j]){
G[i][deg[i]++] = j;
}
maxd = cnt[Find(1)] ;
memset(vis,0,sizeof(vis));
vis[1] = 1;
Count = 0;
dfs(1,1);
printf("There are %d routes from the firestation to streetcorner %d.\n",Count,k);
}
return 0;
}