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;

}