Layout
Time Limit: 1000MS   Memory Limit: 65536K
Total Submissions: 12522   Accepted: 6032

Description

Like everyone else, cows like to stand close to their friends when queuing for feed. FJ has N (2 <= N <= 1,000) cows numbered 1..N standing along a straight line waiting for feed. The cows are standing in the same order as they are numbered, and since they can be rather pushy, it is possible that two or more cows can line up at exactly the same location (that is, if we think of each cow as being located at some coordinate on a number line, then it is possible for two or more cows to share the same coordinate).

Some cows 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 ML (1 <= ML <= 10,000) constraints describes which cows like each other and the maximum distance by which they may be separated; a subsequent list of MD constraints (1 <= MD <= 10,000) tells which cows 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 cow 1 and cow N that satisfies the distance constraints.

Input

Line 1: Three space-separated integers: N, ML, and MD.

Lines 2..ML+1: Each line contains three space-separated positive integers: A, B, and D, with 1 <= A < B <= N. Cows A and B must be at most D (1 <= D <= 1,000,000) apart.

Lines ML+2..ML+MD+1: Each line contains three space-separated positive integers: A, B, and D, with 1 <= A < B <= N. Cows A and B must be at least D (1 <= D <= 1,000,000) apart.

Output

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

Sample Input

4 2 1
1 3 10
2 4 20
2 3 3

Sample Output

27

Hint

Explanation of the sample:

There are 4 cows. Cows #1 and #3 must be no more than 10 units apart, cows #2 and #4 must be no more than 20 units apart, and cows #2 and #3 dislike each other and must be no fewer than 3 units apart.

The best layout, in terms of coordinates on a number line, is to put cow #1 at 0, cow #2 at 7, cow #3 at 10, and cow #4 at 27.

Source

题意:

我认为题意英文正常的都可以看的懂吧。

就是奶牛排队,一个地方可以容纳许多奶牛,

奶牛有互相喜欢的和互相讨厌的,

  先输入喜欢的,1号3号相互喜欢,距离不能超过10

  2和4不能超过20,2,3不能小于3

  对于喜欢输入A,B,C

  就是说d[B]-d[A]<=C;

  转化为,d[B]<=C+d[A];

  求最多,用最短路,下面也需要化成形式一致的才可以。

  不能忘了d[i]-d[i-1]>=0这个限制。

 #include<cstring>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<queue>
#define INF 2000000007
#define N 1007
#define M 10007
using namespace std; int n,l,r;
int dis[N],num[N],ins[N];
int cnt,head[N],next[M*],rea[M*],val[M*]; void add(int u,int v,int fee)
{
next[++cnt]=head[u];
head[u]=cnt;
rea[cnt]=v;
val[cnt]=fee;
}
bool Spfa()
{
for (int i=;i<=n;i++)
ins[i]=,dis[i]=INF,num[i]=;
queue<int>q;
q.push();dis[]=,num[]=;
while(!q.empty())
{
int u=q.front();q.pop();
for (int i=head[u];i!=-;i=next[i])
{
int v=rea[i],fee=val[i];
if (dis[v]>dis[u]+fee)
{
dis[v]=dis[u]+fee;
if (!ins[v])
{
num[v]++;
ins[v]=;
q.push(v);
if (num[v]>n) return false;
}
}
}
ins[u]=;
}
return true;
}
int main()
{
memset(head,-,sizeof(head));
scanf("%d%d%d",&n,&l,&r);
for (int i=,x,y,z;i<=l;i++)
{
scanf("%d%d%d",&x,&y,&z);
add(x,y,z);
}
for (int i=,x,y,z;i<=r;i++)
{
scanf("%d%d%d",&x,&y,&z);
add(y,x,-z);
}
for (int i=;i<=n;i++)
add(i+,i,);
bool flag=Spfa();
if (!flag) printf("-1\n");
else
{
if (dis[n]==INF) printf("-2\n");
else printf("%d\n",dis[n]);
}
}

POJ3169 差分约束 线性的更多相关文章

  1. POJ 3169 Layout(差分约束 线性差分约束)

    题意: 有N头牛, 有以下关系: (1)A牛与B牛相距不能大于k (2)A牛与B牛相距不能小于k (3)第i+1头牛必须在第i头牛前面 给出若干对关系(1),(2) 求出第N头牛与第一头牛的最长可能距 ...

  2. POJ3169(差分约束:转载)

    转载自mengxiang000000传送门 Layout Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 10278   Ac ...

  3. POJ-3169 Layout (差分约束+SPFA)

    POJ-3169 Layout:http://poj.org/problem?id=3169 参考:https://blog.csdn.net/islittlehappy/article/detail ...

  4. [USACO2005][POJ3169]Layout(差分约束)

    题目:http://poj.org/problem?id=3169 题意:给你一组不等式了,求满足的最小解 分析: 裸裸的差分约束. 总结一下差分约束: 1.“求最大值”:写成"<=& ...

  5. poj3169 最短路(差分约束)

    题意:一个农夫有n头牛,他希望将这些牛按照编号 1-n排成一条直线,允许有几头牛站在同一点,但是必须按照顺序,有一些牛关系比较好,希望站的距离不超过某个值,而有一些牛关系不太好,所以希望站的距离大于等 ...

  6. 【POJ3169 】Layout (认真的做差分约束)

    Layout   Description Like everyone else, cows like to stand close to their friends when queuing for ...

  7. 【poj3169】【差分约束+spfa】

    题目链接http://poj.org/problem?id=3169 题目大意: 一些牛按序号排成一条直线. 有两种要求,A和B距离不得超过X,还有一种是C和D距离不得少于Y,问可能的最大距离.如果没 ...

  8. POJ3169:Layout(差分约束)

    Layout Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 15705   Accepted: 7551 题目链接:http ...

  9. POJ 3159 Candies(差分约束+最短路)题解

    题意:给a b c要求,b拿的比a拿的多但是不超过c,问你所有人最多差多少 思路:在最短路专题应该能看出来是差分约束,条件是b - a <= c,也就是满足b <= a + c,和spfa ...

随机推荐

  1. sdut1282Find the Path (floyd变形)

    http://acm.sdut.edu.cn/sdutoj/problem.php?action=showproblem&problemid=1282 感觉这题就比较有意思了 ,虽说是看了别人 ...

  2. framework7 点取消后还提交表单解决方案

    $$('form.ajax-submit').on('submitted', function (e) { var xhr = e.detail.xhr; // actual XHR object v ...

  3. ASP.NET MVC+Bootstrap个人博客之文章打赏(六)

    看到新浪微博.百度百家等等平台上都带有文章“打赏”功能,觉得很新鲜,于是也想在自己的博客中加入“打赏”功能. 当然,加入打赏功能并非是真的想要让别人打赏.因为只有那些真正能引起共鸣,发人深思,让人受益 ...

  4. Uediter的引用和取值

    页面应用Uediter控件,代码如下: <tr> <td align="center" class="xwnr_j"> <asp: ...

  5. JDK集合框架--综述

       接下来的几篇博客总结一下对jdk中常用集合类知识,本篇博客先整体性地介绍一下集合及其主要的api: 从整体上来说,集合分两大类collection和map: 首先来看看Collection: c ...

  6. SQL常用自定义函数

    1.字符串转Table(Func_SplitToTable) CREATE FUNCTION [dbo].[Func_SplitToTable]      (        @SplitString ...

  7. .vue文件在phpstorm中红线解决办法

    主要原因是js版本太低, 1,安装vue.js插件, 2,设置file type,vue.js添加 *.vue, 3,切换js版本为es6,

  8. vue报错-Error: Cannot find module '@babel/core'

    vue之webpack实战的时候遇到报错,Error: Cannot find module '@babel/core' 这报错,我百度了很久,后来发现报错里面有提示,发现是我的 babel-load ...

  9. Unity中,保存在OnInspectorGUI中改变的值

    using UnityEngine; using System.Collections; using UnityEditor; [CustomEditor( typeof( MessageLog ) ...

  10. linux设置ssh连接时间

    相信大家经常遇到SSH连接闲置一会就断开需要重新连接的痛苦,为了使SSH连接保持足够长的时间,我们可以使用如下两种设置 1.sshd服务配置: #vi /etc/ssh/sshd_config Cli ...