Article From:https://www.cnblogs.com/cangT-Tlan/p/9063760.html

# World Exhibition

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1974    Accepted Submission(s):
979

Problem Description
Nowadays, many people want to go to Shanghai to visit
the World Exhibition. So there are always a lot of people who are standing along
a straight line waiting for entering. Assume that there are N (2 <= N <=
1,000) people numbered 1..N who are standing in the same order as they are
numbered. It is possible that two or more person line up at exactly the same
location in the condition that those visit it in a group.

There is
something interesting. Some like each other and want to be within a certain
distance of each other in line. Some really dislike each other and want to be
separated by at least a certain distance. A list of X (1 <= X <= 10,000)
constraints describes which person like each other and the maximum distance by
which they may be separated; a subsequent list of Y constraints (1 <= Y <=
10,000) tells which person dislike each other and the minimum distance by which
they must be separated.

Your job is to compute, if possible, the maximum
possible distance between person 1 and person N that satisfies the distance
constraints.

Input
First line: An integer T represents the case of
test.

The next line: Three space-separated integers: N, X, and Y.

The next X lines: Each line contains three space-separated positive
integers: A, B, and C, with 1 <= A < B <= N. Person A and B must be at
most C (1 <= C <= 1,000,000) apart.

The next Y lines: Each line
contains three space-separated positive integers: A, B, and C, with 1 <= A
< B <= C. Person A and B must be at least C (1 <= C <= 1,000,000)
apart.

Output
For each line: A single integer. If no line-up is
possible, output -1. If person 1 and N can be arbitrarily far apart, output -2.
Otherwise output the greatest possible distance between person 1 and N.

Sample Input
1
4 2 1
1 3 8
2 4 15
2 3 4

Sample Output
19

Author
alpc20

Source
2010
ACM-ICPC Multi-University Training Contest（15）——Host by NUDT

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Idea: the same thing as the last one.
```#include<queue>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define MAXN 1000010
using namespace std;
queue<int>que;
int n,x,y,t,tot;
int vis[MAXN],dis[MAXN],cnt[MAXN];
}
void spfa(){
memset(cnt,0,sizeof(cnt));
memset(vis,0,sizeof(vis));
memset(dis,0x7f,sizeof(dis));
while(!que.empty())    que.pop();
dis[1]=0;vis[1]=1;
cnt[1]=1;que.push(1);
while(!que.empty()){
int now=que.front();
que.pop();vis[now]=0;
if(dis[to[i]]>dis[now]+cap[i]){
dis[to[i]]=dis[now]+cap[i];
if(!vis[to[i]]){
if(++cnt[to[i]]>n){ printf("-1\n");return ; }
vis[to[i]]=1;
que.push(to[i]);
}
}
}
if(dis[n]==2139062143)    printf("-2\n");
else printf("%d\n",dis[n]);
}
int main(){
scanf("%d",&t);
while(t--){
scanf("%d%d%d",&n,&x,&y);
for(int i=1;i<=x;i++){
int a,b,d;
scanf("%d%d%d",&a,&b,&d);
}
for(int i=1;i<=y;i++){
int a,b,d;
scanf("%d%d%d",&a,&b,&d);
}
}
}
/*
2
4 2 1
1 3 8
2 4 15
2 3 4
4 2 1
1 3 10
2 4 20
2 3 3
*/```