Firetruck（UVA 208）

测评传送门

---

思路：

这是道独流搜索，题目出的很好，输出给毁了。一定注意！！不要多打空格！！！

由于图会过于稠密，所以我们需要通过并查集剪枝，看从起点能不能到终点

code

#include<stdio.h> 
#include<string.h>
#include<vector>
#include<algorithm> 
using namespace std;
const int MXN=25;
vector<int> v[MXN];
int n,fire,ub,ans;
int fa[MXN],rout[MXN];
bool vis[MXN];

void ycl() 
{
    for(int i=1;i<=MXN;++i) {
        v[i].clear();
        fa[i]=i;
    }
}

int Find(int x) {
    return x==fa[x]?x:fa[x]=Find(fa[x]);
}

void dfs(int x,int pos) 
{
    rout[pos]=x;
    if(x==fire) {
        ans++;
        printf("%d",rout[1]);
        for(int i=2;i<=pos;++i) {
            printf(" %d",rout[i]);
        }
        printf("
");
        return ;
    }
    for(int i=0;i<v[x].size();++i) {
        int to=v[x][i];
        if(!vis[to]) {
            vis[to]=1;
            dfs(to,pos+1);
            vis[to]=0;
        }
    }
}

int main() 
{
    int cas=0;
    while(scanf("%d",&fire)!=EOF) 
    {
        ycl();
        int from,to;
        while(scanf("%d%d",&from,&to) && from && to) {
            v[from].push_back(to);
            v[to].push_back(from);
            fa[Find(from)]=Find(to);
            ub=max(ub,max(from,to));
        }
        ans=0;
        printf("CASE %d:
",++cas);
        if(Find(1)!=Find(fire)) {
            printf("There are %d routes from the firestation to streetcorner %d.
",0,fire);
        }
        else {
            for(int i=1;i<=ub;++i) {
                if(v[i].size()) {
                    sort(v[i].begin(),v[i].end());
                }
            }
            memset(vis,0,sizeof(vis));
            vis[1]=1;
            dfs(1,1);
            printf("There are %d routes from the firestation to streetcorner %d.
",ans,fire);
        }
    }
}
/*
6
1 2
1 3
3 4
3 5
4 6
5 6
2 3
2 4
0 0
4
2 3
3 4
5 1
1 6
7 8
8 9
2 5
5 7
3 1
1 8
4 6
6 9
0 0
*/