Sgu 103

容易想到，对于某个顶点，先到达总不会比后到达要差，因此本题可用贪心算法，联系图论中的最短路求法，本题可采用dijkstra算法，难点主要在边权的计算上，详见windywinter牛的题解： http://www.briefdream.com/sgu-103/。

  1 #include<stdio.h>
  2 #include<stdlib.h>
  3 #include<string.h>
  4 struct news
  5 {
  6     int r,tb,tp,c;
  7 } juc[301];
  8 struct color
  9 {
 10     int c,t;
 11 };
 12 int map[301][301],dis[301],pre[301],start,end,n,m;
 13 bool reach[301];
 14 int ans[301],ansnum;
 15 int min(int a, int b)
 16 {
 17     return a>b?b:a;
 18 }
 19 void init()
 20 {
 21     scanf("%d %d\n%d %d\n",&start,&end,&n,&m);
 22     for(int i=1;i<=n;++i)
 23     {
 24         char tmp;
 25         scanf("%c %d %d %d\n",&tmp,&juc[i].r,&juc[i].tb,&juc[i].tp);
 26         juc[i].c=tmp=='B'?0:1;
 27     }
 28     for(int i=1;i<=m;++i)
 29     {
 30         int x,y,z;
 31         scanf("%d %d %d",&x,&y,&z);
 32         map[x][y]=map[y][x]=z;
 33     }
 34 }
 35 color calccolor(int id, int nowtime)
 36 {
 37     color ans;
 38     int r=juc[id].r,tb=juc[id].tb,tp=juc[id].tp;
 39     if(nowtime<r)
 40     {
 41         ans.c=juc[id].c;
 42         ans.t=r-nowtime;
 43     }
 44     else if(!juc[id].c)
 45     {
 46         if(ans.c=(nowtime-r)%(tb+tp)<tp)
 47             ans.t=tp-(nowtime-r)%(tb+tp);
 48         else
 49             ans.t=tb+tp-(nowtime-r)%(tb+tp);
 50     }
 51     else
 52     {
 53         if(ans.c=(nowtime-r)%(tb+tp)>=tb)
 54             ans.t=tb+tp-(nowtime-r)%(tb+tp);
 55         else
 56             ans.t=tb-(nowtime-r)%(tb+tp);
 57     }
 58     return ans;
 59 }
 60 int calc(int starttime, int fromid, int toid, int flag)
 61 {
 62     if(flag>3) return -1;
 63     color from,to;
 64     from=calccolor(fromid,starttime);
 65     to=calccolor(toid,starttime);
 66     if(from.c==to.c) return starttime;
 67     if(from.t==to.t) return calc(starttime+from.t,fromid,toid,flag+1);
 68     return starttime+min(from.t,to.t);
 69 }
 70 void work()// dijkstra
 71 {
 72     bool vis[301]={false};
 73     memset(dis,0x77,sizeof(dis));
 74     dis[start]=0;
 75     pre[start]=-1;
 76     reach[start]=true;
 77     int leftnum=n;
 78     while(leftnum)
 79     {
 80         int mindis=99999999,now;
 81         for(int i=1;i<=n;++i) if(!vis[i])
 82             if(dis[i]<mindis)
 83             {
 84                 now=i;
 85                 mindis=dis[i];
 86             }
 87         --leftnum;
 88         vis[now]=true;
 89         for(int i=1;i<=n;++i) if(map[now][i])
 90         {
 91             int tmp=calc(dis[now],now,i,1);
 92             if(tmp==-1) continue;
 93             tmp+=map[now][i];
 94             if(tmp<dis[i])
 95             {
 96                 dis[i]=tmp;
 97                 pre[i]=now;
 98                 reach[i]=true;
 99             }
100         }
101     }
102 }
103 void print()
104 {
105     if(!reach[end])
106     {
107         printf("0\n");
108         return;
109     }
110     printf("%d\n",dis[end]);
111     int now=end;
112     while(now!=-1)
113     {
114         ans[++ansnum]=now;
115         now=pre[now];
116     }
117     printf("%d",ans[ansnum]);
118     for(int i=ansnum-1;i>=1;--i)
119         printf(" %d",ans[i]);
120     printf("\n");
121 }
122 int main()
123 {
124     init();
125     work();
126     print();
127     return 0;
128 }