UVa11374 Airport Express

来源：互联网发布：c语言游戏编程入门编辑：程序博客网时间：2024/04/30 08:03
题目描述传送门
正反向Dijkstra,枚举商业线。
坑点：最后输出路径，格式。
代码
#include<cstdio>#include<iostream>#include<cstring>#include<algorithm>#include<queue>#include<stack>using namespace std;const int maxn=505,maxm=1005;const int INF=1e9;int n,s,e,m,x,y,z,k;struct Edge{    int t,d,nxt;    Edge(int a=0,int b=0,int c=0):t(a),d(b),nxt(c){}}edges[maxm*2];struct heap{    int d,v;    heap(int a=0,int b=0):d(a),v(b){}    bool operator<(const heap&a)const{        return d>a.d;    }};int h[maxn],cnt,d1[maxn],d2[maxn],p1[maxn],p2[maxn];bool vis[maxn];void addedge(int from,int to,int dist){    edges[++cnt]=Edge(to,dist,h[from]);    h[from]=cnt;    edges[++cnt]=Edge(from,dist,h[to]);    h[to]=cnt;}int main(){    bool case1=1;    while(scanf("%d %d %d",&n,&s,&e)!=EOF){        cnt=0;        scanf("%d",&m);        if(!case1) puts("");        else case1=0;        memset(h,0,sizeof(h));        for(int i=0;i<m;i++){            scanf("%d%d%d",&x,&y,&z);            addedge(x,y,z);        }        for(int i=1;i<=n;i++) d1[i]=d2[i]=INF;        priority_queue<heap>q;        memset(vis,0,sizeof(vis));        q.push(heap(0,s));        d1[s]=0;        while(!q.empty()){            heap x=q.top();q.pop();            int u=x.v;            if(vis[u]) continue;            vis[u]=1;            for(int i=h[u];i;i=edges[i].nxt){                int v=edges[i].t;                if(d1[u]+edges[i].d<d1[v]){                    d1[v]=d1[u]+edges[i].d;                    p1[v]=u;                    q.push(heap(d1[v],v));                }            }        }           memset(vis,0,sizeof(vis));        q.push(heap(0,e));        d2[e]=0;        while(!q.empty()){            heap x=q.top();q.pop();            int u=x.v;            if(vis[u]) continue;            vis[u]=1;            for(int i=h[u];i;i=edges[i].nxt){                int v=edges[i].t;                if(d2[u]+edges[i].d<d2[v]){                    d2[v]=d2[u]+edges[i].d;                    p2[v]=u;                    q.push(heap(d2[v],v));                }            }        }        cin>>k;        int ans=d1[e],ansx=-1,ax,ay,o;        for(int i=0;i<k;i++){            scanf("%d%d%d",&x,&y,&z);            int a=d1[x]+d2[y]+z,b=d1[y]+d2[x]+z,k,nx=x,ny=y;            if(a<b) k=a;            else k=b,swap(nx,ny);            if(k<ans) ans=k,ansx=nx,ax=nx,ay=ny;        }        if(ansx==-1){            stack<int> stk;            int k=e;            for(;;){                stk.push(k);                if(k==s) break;                k=p1[k];            }            while(!stk.empty()) printf("%d%c",stk.top(),stk.top()==e?'\n':' '),stk.pop();            puts("Ticket Not Used");        }        else{            stack<int> stk;            int k=ax;            for(;;){                stk.push(k);                if(k==s) break;                k=p1[k];            }            while(!stk.empty()) printf("%d ",stk.top()),stk.pop();            k=ay;            for(;;){                printf("%d%c",k,k==e?'\n':' ');                if(k==e) break;                k=p2[k];            }            printf("%d\n",ansx);        }        printf("%d\n",ans);    }}
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