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 numbe…

Layout Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 15705   Accepted: 7551 题目链接:http://poj.org/problem?id=3169 Description: Like everyone else, cows like to stand close to their friends when queuing for feed. FJ has N (2 <= N <= 1,00…

题目链接:http://poj.org/problem?id=3169 差分约束的解释:http://www.cnblogs.com/void/archive/2011/08/26/2153928.html 我也不是特别理解,要是给你a - b <= k 就建一条b->a权值为k的有向边,要是a - b >= k 就建一条a -> b边权是-k的有向边,要是让你求n到1的最大差,就是让你求1到n的最短距离. 差分约束系统有两种方式可以求解,最短路和最长路.当我们把不等式整理成d[a…

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"<=",求最短路 2.“求最小值”:写成">=",求最长路…

POJ-3169 Layout:http://poj.org/problem?id=3169 参考:https://blog.csdn.net/islittlehappy/article/details/81155802 题意: 一共有n头牛,有ml个关系好的牛的信息,有md个关系不好的牛的信息,对应输入的第一行的三个元素,接下来ml行,每行三个元素A,B,D,表示A牛和B牛相距不希望超过D,接下来md行,每行三个元素A,B,D表示A牛和B牛的相距至少要有D才行.求1号牛和n号牛的最大距离,如果…

POJ3169 Layout 题意: n头牛编号为1到n,按照编号的顺序排成一列,每两头牛的之间的距离 >= 0.这些牛的距离存在着一些约束关系:1.有ml组(u, v, w)的约束关系,表示牛[u]和牛[v]之间的距离必须 <= w.2.有md组(u, v, w)的约束关系,表示牛[u]和牛[v]之间的距离必须 >= w.问如果这n头无法排成队伍,则输出-1,如果牛[1]和牛[n]的距离可以无限远,则输出-2,否则则输出牛[1]和牛[n]之间的最大距离. 分析: 记第i号牛的位置是d[…

O - Layout(差分约束 + spfa) 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 the…

Did Pong Lie? 时间限制: 5 Sec  内存限制: 128 MB提交: 68  解决: 15[提交][状态][讨论版] 题目描述 Doctor Pong has two arrays of integers : a1 , a2 , ......, aN and b1 , b2 , ......, bM . His student Rong wants to know what these numbers are, but Pong won’t tell him the number…

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 numbe…

<题目链接> 题目大意: 一些母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.如果没有最大距离输出-1,如果1.n之间距离任意就输出-2,否则输出最大的距离. 解题分析:典型的差分约束,第一种约束,v-u<=c:第二种约束:v-u>=c  可以转化为 u-v<=c ,还有一种约束,因为题目要求按序号排序,所以 loc[i] - loc[i-1]>=0 ,即 loc[i-1]-loc[i]<=0 .以上就是…