Is the Information Reliable?
| Time Limit: 3000MS | Memory Limit: 131072K | |
| Total Submissions: 11125 | Accepted: 3492 |
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 Reliabl
给出了 P a b w 表示 b在a以北w公里， V a b 表示 b在a北边，最少1公里，问所有 的条件可不可以全部满足。
由P 可以得到 b - a = w 也就是b - a <= w && a - b <= w ，由 V a b 得到 b - a >= 1 也就是 a - b <= -1 ;建图，使用最短路，判断是否会有负环。初始dis要全部为0.
#include <cstdio>
#include <cstring>
#include <algorithm>
struct node
{
int u , v , w ;
} p[300000];
int dis[2000] , cnt ;
void add(int u,int v,int w)
{
p[cnt].u = u ;
p[cnt].v = v ;
p[cnt++].w = w ;
}
int main()
{
int i , j , n , m , u , v , w ;
char str[10] ;
while(scanf("%d %d", &n, &m)!=EOF)
{
cnt = 0 ;
while(m--)
{
scanf("%s", str);
if(str[0] == 'P')
{
scanf("%d %d %d", &u, &v, &w);
add(u,v,-w);
add(v,u,w);
}
else
{
scanf("%d %d", &u, &v);
add(u,v,-1);
}
}
memset(dis,0,sizeof(dis));
for(i = 1 ; i <= n ; i++)
for(j = 0 ; j < cnt ; j++)
if( dis[ p[j].v ] >dis[ p[j].u ] + p[j].w )
dis[ p[j].v ] = dis[ p[j].u ] + p[j].w ;
for(j = 0 ; j < cnt ; j++)
if( dis[ p[j].v ] > dis[ p[j].u ] + p[j].w )
break;
if(j < cnt)
printf("Unreliable\n");
else
printf("Reliable\n");
}
}