bzoj1611 / P2895 [USACO08FEB]流星雨Meteor Shower

P2895 [USACO08FEB]流星雨Meteor Shower

给每个点标记一下能够走的最迟时间，蓝后bfs处理一下

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<cctype>
 #include<queue>
 #define re register
 using namespace std;
 void read(int &x){
     char c=getchar();x=;
     while(!isdigit(c)) c=getchar();
     while(isdigit(c)) x=(x<<)+(x<<)+(c^),c=getchar();
 }
 int min(int a,int b){return a<b?a:b;}
 #define N 310
 const int d1[]={,,-,,};
 const int d2[]={,,,-,};
 struct node{int x,y,t;}a;
 queue <node> h;
 int m,tp=,ans,dan[N][N],win; bool vis[N][N];
 int main(){
     memset(dan,,sizeof(dan)); int inf=dan[][];
     read(m);
     for(re int i=;i<=m;++i){
         read(a.x);read(a.y);read(a.t);
         ++a.x; ++a.y;
         dan[a.x][a.y]=min(dan[a.x][a.y],a.t);
         dan[a.x][a.y+]=min(dan[a.x][a.y+],a.t);
         dan[a.x][a.y-]=min(dan[a.x][a.y-],a.t);
         dan[a.x+][a.y]=min(dan[a.x+][a.y],a.t);
         dan[a.x-][a.y]=min(dan[a.x-][a.y],a.t);
     }//处理每个点能走的最迟时间
     h.push((node){,,}); vis[][]=;
     if(dan[][]==inf) win=,ans=;
     while(!h.empty()&&!win){
         node u=h.front(); h.pop();
         for(re int i=;i<&&!win;++i){
             int r1=u.x+d1[i],r2=u.y+d2[i];
             if(r1<||r2<||r1>=N||r2>=N) continue;
             if(vis[r1][r2]||dan[r1][r2]<=u.t+) continue;
             if(dan[r1][r2]==inf) win=,ans=u.t+;
             else h.push((node){r1,r2,u.t+}),vis[r1][r2]=;
         }
     }win ? printf("%d",ans):printf("-1");
     return ;
 }