HDU 1596——find the safest road

最小生成树

dij算法就可解决。

#include<cstdio>#include<cstring>#include<iostream>using namespace std;#define maxn 1005double map[maxn][maxn],dis[maxn];bool que[maxn];int main(){int n,i,j;while(scanf("%d",&n)!=EOF){for(i=1;i<=n;i++)for(j=1;j<=n;j++)scanf("%lf",&map[i][j]);int t,s,e,k;double temp;scanf("%d",&t);while(t--){scanf("%d%d",&s,&e);memset(que,0,sizeof(que));for(i=1;i<=n;i++)dis[i]=map[s][i];que[s]=1;dis[s]=1;for(i=1;i<=n;i++){temp=0.0;for(j=1;j<=n;j++)if(!que[j]&&temp<dis[j]){temp=dis[j];k=j;}if(temp==0)break;if(que[e])break;que[k]=1;for(j=1;j<=n;j++)if(!que[j]&&dis[j]<dis[k]*map[k][j])dis[j]=dis[k]*map[k][j];}if(dis[e]==0.0)printf("What a pity!\n");elseprintf("%.3lf\n",dis[e]);}}return 0;}