紫书搜索 习题7-1 UVA

题目链接:

https://vjudge.net/problem/UVA-208

题意:

题解:

代码:

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define MS(a) memset(a,0,sizeof(a))
#define MP make_pair
#define PB push_back
const int INF = 0x3f3f3f3f;
const ll INFLL = 0x3f3f3f3f3f3f3f3fLL;
inline ll read(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
//////////////////////////////////////////////////////////////////////////
const int maxn = 1e5+10;

int k,vis[30],vis2[30],road[30],sum;
vector<int> G[maxn];

bool bfs(){
    queue<int> q;
    q.push(1); vis[1] = 1;

    while(!q.empty()){
        int u = q.front(); q.pop();
        if(u == k) return true;
        for(int i=0; i<(int)G[u].size(); i++){
            int v = G[u][i];
            if(!vis[v]) {
                q.push(v);
                vis[v] = 1;
            }
        }
    }
    return false;
}

void dfs(int cur,int u){
    road[cur] = u;
    if(u == k){
        printf("%d", road[1]);
        for(int i=2; i<=cur; i++)
            printf(" %d", road[i]);
        puts("");
        sum ++;
        return ;
    }

    for(int i=0; i<(int)G[u].size(); i++){
        int v = G[u][i];
        if(!vis2[v]){
            vis2[v] = 1;
            dfs(cur+1,v);
            vis2[v] = 0;
        }
    }
}

int main(){
    int cas = 1;
    while(scanf("%d",&k) == 1){
        MS(vis); MS(vis2);
        for(int i=0; i<=20; i++) G[i].clear();
        sum = 0;
        int u,v;
        while(scanf("%d%d",&u,&v) && (u+v)){
            G[u].push_back(v);
            G[v].push_back(u);
        }

        for(int i=0; i<=20; i++)
            sort(G[i].begin(),G[i].end());

        printf("CASE %d:
",cas++);
        vis2[1] = 1;
        if(bfs())  dfs(1,1);
        printf("There are %d routes from the firestation to streetcorner %d.
",sum,k);
    }

    return 0;
}