锐客网

  1. 首页 > it技术 > >

小白书训练计划|UVa10986_Sending email(最短路)(小白书图论专题)

解题报告
思路：
裸裸的最短路。

#include #include #include #include #define inf 0x3f3f3f3f #define N 40000 #define M 100000 using namespace std; struct node { int v,w,next; }edge[M]; int head[N],dis[N],vis[N],cnt,n,m,s,t; void add(int u,int v,int w) { edge[cnt].v=v; edge[cnt].w=w; edge[cnt].next=head[u]; head[u]=cnt++; } void spfa() { for(int i=0; iQ; Q.push(s); while(!Q.empty()){ int u=Q.front(); Q.pop(); vis[u]=0; for(int i=head[u]; i!=-1; i=edge[i].next) { int v=edge[i].v; if(dis[v]>dis[u]+edge[i].w) { dis[v]=dis[u]+edge[i].w; if(!vis[v]) { vis[v]=1; Q.push(v); } } } } } int main() { int i,j,T,u,v,w,k=1; scanf("%d",&T); while(T--) { memset(head,-1,sizeof(head)); cnt=0; scanf("%d%d%d%d",&n,&m,&s,&t); for(i=0; i


Problem E
Sending email
Time Limit: 3 seconds

"A new internet watchdog is creating a stir in
Springfield. Mr. X, if that is his real name, has
come up with a sensational scoop."
Kent Brockman
There are n SMTP servers connected by network cables. Each of the m cables connects two computers and has a certain latency measured in milliseconds required to send an email message. What is the shortest time required to send a message from server S to server T along a sequence of cables? Assume that there is no delay incurred at any of the servers.
Input
The first line of input gives the number of cases, N. N test cases follow. Each one starts with a line containing n(2<=n<20000), m (0<=m<50000), S (0<=S Output
For each test case, output the line "Case #x:" followed by the number of milliseconds required to send a message from S toT. Print "unreachable" if there is no route from S to T.
Sample Input Sample Output
3 2 1 0 1 0 1 100 3 3 2 0 0 1 100 0 2 200 1 2 50 2 0 0 1

Case #1: 100 Case #2: 150 Case #3: unreachable

【小白书训练计划|UVa10986_Sending email(最短路)(小白书图论专题)】
Problemsetter: Igor Naverniouk

    推荐阅读


    上一篇：POJ训练计划|POJ训练计划2528_Mayor's posters(线段树/成段更新+离散化)

    下一篇：基带调制和射频调制