POJ 2983 Is the Information Reliable?-优快云博客

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Is the Information Reliable?

Time Limit: 3000MS		Memory Limit: 131072K
Total Submissions: 11148		Accepted: 3500

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

Sample Output

Unreliable
Reliable

题目的意思是：当输入为P时，输入三个数，a-b=c，即a-b>=c&&b-a<=c;

当输入为V时，a与b的距离>=1;

求最长路，若存在最长路，则输出Unreliable

<span style="font-size:18px;">#include <iostream>
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<stdlib.h>
using namespace std;
int inf=10000000;
struct node
{
    int u,v,w;
} edge[200001];
int dis[200001];
int n,m,cnt;
int bf()
{
    int flag;
    int i,j;
    memset(dis,0,sizeof(dis));
    for(i=1; i<=n; i++)
    {
        flag=0;
        for(j=0; j<cnt; j++)
        {
            if(dis[edge[j].u]<dis[edge[j].v]+edge[j].w)
            {
                dis[edge[j].u]=dis[edge[j].v]+edge[j].w;
                flag=1;
            }
        }
        if(flag==0)
            break;
    }
    if(flag) printf("Unreliable\n");
    else
        printf("Reliable\n");
}
int main()
{
    int i,j,a,b,c,d,e;
    char ch;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        cnt=0;
        for(i=1; i<=m; i++)
        {
            getchar();
            scanf("%c",&ch);
            if(ch=='P')
            {
                scanf("%d%d%d",&a,&b,&c);
                edge[cnt].u=a;
                edge[cnt].v=b;
                edge[cnt].w=c;
                cnt++;

                edge[cnt].u=b;
                edge[cnt].v=a;
                edge[cnt].w=-c;
                cnt++;
            }
            else
            {
                scanf("%d%d",&d,&e);
                edge[cnt].u=d;
                edge[cnt].v=e;
                edge[cnt].w=1;
                cnt++;
            }
        }
        bf();
    }
    return 0;
}











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