bzoj1641 / P2888 [USACO07NOV]牛栏Cow Hurdles

P2888 [USACO07NOV]牛栏Cow Hurdles

Floyd

$n<=300$？果断Floyd

给出核心式，自行体会

$d[i][j]=min(d[i][j],max(d[i][k],d[k][j]))$

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 using namespace std;
 int max(int a,int b){return a>b?a:b;}
 int min(int a,int b){return a<b?a:b;}
 int d[][],n,m,t;
 int main(){
     memset(d,,sizeof(d));
     scanf("%d%d%d",&n,&m,&t);
     for(int i=,q1,q2,q3;i<=m;++i){
         scanf("%d%d%d",&q1,&q2,&q3);
         d[q1][q2]=q3;
     }
     for(int k=;k<=n;++k)
         for(int i=;i<=n;++i)
             for(int j=;j<=n;++j)
                 d[i][j]=min(d[i][j],max(d[i][k],d[k][j]));
     for(int i=,q1,q2;i<=t;++i){
         scanf("%d%d",&q1,&q2);
         if(d[q1][q2]==d[][]) printf("-1\n");
         else printf("%d\n",d[q1][q2]);
     }return ;
 }