POJ 之 Is the Information Reliable?

B - Is the Information Reliable?

Time Limit:3000MS     Memory Limit:131072KB     64bit IO Format:%I64d & %I64u

Submit Status

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

#include <stdio.h>
#include <string.h>

int n, m;
int dis[1003];
int cnt;
struct N
{
    int u;
    int v;
    int w;
}s[200003];

void add(int u, int v, int w )
{
    s[cnt].u=u;
    s[cnt].v=v;
    s[cnt++].w=w;
}

void bellman_ford()
{
    memset(dis, 0, sizeof(dis));
    int i, j;
    for(i=1; i<=n; i++)
    {
        for(j=0; j<cnt; j++) //检查每条边
        {
            if( dis[s[j].v] > dis[s[j].u] + s[j].w )
                dis[s[j].v] = dis[s[j].u]+s[j].w ;
        }
    }
    for(i=0; i<cnt; i++)
    {
        if(dis[s[i].v] > dis[s[i].u]+s[i].w )
        break;
    }
    if(i<cnt)
        printf("Unreliable\n");
    else
        printf("Reliable\n");
}

int main()
{
    int i, j;
    char ch;
    int u, v, w;

    while(scanf("%d %d%*c", &n, &m)!=EOF)
    {
        cnt=0;
        for(i=0; i<m; i++ )
        {
            ch=getchar();
            while(ch!='P' && ch!='V')
            {
                ch=getchar();
            }
            if(ch=='P')
            {
                scanf("%d %d %d", &u, &v, &w );
                add(u, v, -1*w);
                add(v, u, w);
            }
            else
            {
                scanf("%d %d", &u, &v );
                add(u, v, -1 );
            }
        }
        bellman_ford();
    }
    return 0;
}