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| Time Limit: 3000MS | Memory Limit: 131072K | |
| Total Submissions: 11859 | Accepted: 3742 |
Description
The galaxy war between the Empire Draco and the Commonwealth of Zibu broke out 3 years ago. Draco established a line of defense called Grot. Grot is a straight line with N defense stations. Because of the cooperation of the stations, Zibu’s Marine Glory cannot march any further but stay outside the line.
A mystery Information Group X benefits form selling information to both sides of the war. Today you the administrator of Zibu’s Intelligence Department got a piece of information about Grot’s defense stations’ arrangement from Information Group X. Your task is to determine whether the information is reliable.
The information consists of M tips. Each tip is either precise or vague.
Precise tip is in the form of P A B X, means defense station A is X light-years north of defense station B.
Vague tip is in the form of V A B, means defense station A is in the north of defense station B, at least 1 light-year, but the precise distance is unknown.
Input
There are several test cases in the input. Each test case starts with two integers N (0 < N ≤ 1000) and M (1 ≤ M ≤ 100000).The next M line each describe a tip, either in precise form or vague form.
Output
Output one line for each test case in the input. Output “Reliable” if It is possible to arrange N defense stations satisfying all the M tips, otherwise output “Unreliable”.
Sample Input
3 4 P 1 2 1 P 2 3 1 V 1 3 P 1 3 1 5 5 V 1 2 V 2 3 V 3 4 V 4 5 V 3 5
Sample Output
Unreliable Reliable
Source
POJ Monthly--2006.08.27, Dagger
http://blog.csdn.net/lyy289065406/article/details/6648688
ac代码
#include<stdio.h>
#include<string.h>
#include<queue>
#include<string>
#include<iostream>
#define INF 0xfffffff
using namespace std;
int head[1010],vis[1010],cnt,dis[1010],s,cot[1010];
int n,m;
struct s
{
int u,v,w,next;
}edge[300200];
void add(int u,int v,int w)
{
edge[cnt].u=u;
edge[cnt].v=v;
edge[cnt].w=w;
edge[cnt].next=head[u];
head[u]=cnt++;
}
int spfa(int s)
{
int i;
for(i=1;i<=n;i++)
{
dis[i]=INF;
}
memset(vis,0,sizeof(vis));
memset(cot,0,sizeof(cot));
dis[s]=0;
vis[s]=1;
queue<int>q;
q.push(s);
while(!q.empty())
{
int u=q.front();
q.pop();
vis[u]=0;
cot[u]++;
if(cot[u]>n)
return 0;
for(i=head[u];i!=-1;i=edge[i].next)
{
int v=edge[i].v;
int w=edge[i].w;
if(dis[v]>dis[u]+w)
{
dis[v]=dis[u]+w;
if(!vis[v])
{
vis[v]=1;
q.push(v);
}
}
}
}
return 1;
}
int main()
{
// int n,m;
while(scanf("%d%d",&n,&m)!=EOF)
{
char str[2];
int i;
memset(head,-1,sizeof(head));
cnt=0;
for(i=0;i<m;i++)
{
scanf("%s",str);
if(str[0]=='P')
{
int a,b,c;
scanf("%d%d%d",&a,&b,&c);
add(a,b,c);
add(b,a,-c);
}
else
{
int a,b;
scanf("%d%d",&a,&b);
add(b,a,-1);
}
}
s=n+1;
for(i=1;i<=n;i++)
{
add(s,i,0);
}
if(spfa(s))
printf("Reliable\n");
else
printf("Unreliable\n");
}
}版权声明：本文为博主原创文章，未经博主允许不得转载。
POJ 题目2983 Is the Information Reliable?（差分约束）
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原文地址：http://blog.csdn.net/yu_ch_sh/article/details/46931167
