博客
关于我
强烈建议你试试无所不能的chatGPT,快点击我
find the longest of the shortest (hdu 1595 SPFA+枚举)
阅读量:6791 次
发布时间:2019-06-26

本文共 3627 字,大约阅读时间需要 12 分钟。

find the longest of the shortest

Time Limit: 1000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1916    Accepted Submission(s): 668


Problem Description
Marica is very angry with Mirko because he found a new girlfriend and she seeks revenge.Since she doesn't live in the same city, she started preparing for the long journey.We know for every road how many minutes it takes to come from one city to another.
Mirko overheard in the car that one of the roads is under repairs, and that it is blocked, but didn't konw exactly which road. It is possible to come from Marica's city to Mirko's no matter which road is closed.
Marica will travel only by non-blocked roads, and she will travel by shortest route. Mirko wants to know how long will it take for her to get to his city in the worst case, so that he could make sure that his girlfriend is out of town for long enough.Write a program that helps Mirko in finding out what is the longest time in minutes it could take for Marica to come by shortest route by non-blocked roads to his city.
 

Input
Each case there are two numbers in the first row, N and M, separated by a single space, the number of towns,and the number of roads between the towns. 1 ≤ N ≤ 1000, 1 ≤ M ≤ N*(N-1)/2. The cities are markedwith numbers from 1 to N, Mirko is located in city 1, and Marica in city N.
In the next M lines are three numbers A, B and V, separated by commas. 1 ≤ A,B ≤ N, 1 ≤ V ≤ 1000.Those numbers mean that there is a two-way road between cities A and B, and that it is crossable in V minutes.
 

Output
In the first line of the output file write the maximum time in minutes, it could take Marica to come to Mirko.
 

Sample Input
 
5 6 1 2 4 1 3 3 2 3 1 2 4 4 2 5 7 4 5 1 6 7 1 2 1 2 3 4 3 4 4 4 6 4 1 5 5 2 5 2 5 6 5 5 7 1 2 8 1 4 10 2 3 9 2 4 10 2 5 1 3 4 7 3 5 10
 

Sample Output
 
11 13 27
 
先求整个的最短路,并记录下最短路经,再分别枚举删除最短路经上的每一条边。并再次求最短路,答案即最长的那条最短路。

代码:
#include 
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#pragma comment (linker,"/STACK:102400000,102400000")#define maxn 1010#define MAXN 2005#define mod 1000000009#define INF 0x3f3f3f3f#define pi acos(-1.0)#define eps 1e-6typedef long long ll;using namespace std;struct Edge{ int v,w; int next;}edge[maxn*maxn];int head[maxn],inq[maxn],inqtime[maxn],dist[maxn];int path[maxn];int N,num,m,a[maxn],ok;bool flag[maxn];void addedge(int u,int v,int w){ edge[num].v=v; edge[num].w=w; edge[num].next=head[u]; head[u]=num++; edge[num].v=u; edge[num].w=w; edge[num].next=head[v]; head[v]=num++;}int SPFA(int s,int n){ int i; memset(inq,0,sizeof(inq)); memset(dist,INF,sizeof(dist)); if (ok) { for (int i=0;i<=n;i++) path[i]=-1; } path[s]=0; queue
Q; inq[s]=1; dist[s]=0; Q.push(s); while (!Q.empty()) { int u=Q.front(); Q.pop(); inq[u]=0; for (i=head[u];i;i=edge[i].next) { if (dist[ edge[i].v ]>dist[u]+edge[i].w) { if (ok) path[ edge[i].v ]=u; dist[ edge[i].v ]=dist[u]+edge[i].w; if (!inq[ edge[i].v ]) { inq[ edge[i].v ]=1; Q.push(edge[i].v); } } } } return dist[N];}int main(){ int i,j; while (~scanf("%d%d",&N,&m)) { int u,v,w; memset(head,0,sizeof(head)); num=1; ok=1; for (i=0;i
0) { int x,y,value; for (int i=head[j];i!=0;i=edge[i].next) { if (edge[i].v==path[j]) { x=i; value=edge[i].w; edge[i].w=INF; break; } } for (int i=head[path[j]];i!=0;i=edge[i].next) { if (edge[i].v==j) { y=i; edge[i].w=INF; break; } } ans=max(ans,SPFA(1,N)); edge[x].w=value; edge[y].w=value;// printf("j=%d\n",j); j=path[j]; }// printf("\n%d\n",path[1]); printf("%d\n",ans); } return 0;}

转载地址:http://kkogo.baihongyu.com/

你可能感兴趣的文章
php function
查看>>
ubuntu 开机启动时自动运行程序
查看>>
Windows查看文件句柄
查看>>
端午骑行活动照
查看>>
alpine下安装swoole失败
查看>>
ttyd -- 分享任意命令行程序到网页上
查看>>
模态窗口的关闭确认和事件执行
查看>>
php时间处理函数
查看>>
VirtualBox虚拟机安装CentOS 7图文教程
查看>>
深入类的初始化和方法重载(一)
查看>>
如何在Ubuntu上创建Node.js Addon
查看>>
linux后台运行程序(secureCRT断掉或关闭后继续运行程序)
查看>>
Android组件化开发实践和案例分享
查看>>
我的网站搭建 (第七天) 简单阅读计数
查看>>
正则表达式常用的算法
查看>>
Mybatis3.3.x技术内幕(十):Mybatis初始化流程(下)
查看>>
OpenGl的glMatrixMode()函数理解
查看>>
在IDEA中使用SpringBoot整合MyBatis和Thymeleaf
查看>>
SpringMVC统一异常处理简单配置
查看>>
Scala的List,View, Iterator, Stream的一点差别
查看>>