UVA1464 Traffic Real Time Query System

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UVA1464 Traffic Real Time Query System

传送门:https://www.luogu.com.cn/problem/UVA1464 看到这道题,求必经的点数,还是无向图.那么妥妥的圆方树.圆方树上的任意两圆点间的路径必定是圆点方点相交错的,对于树上的两点来说,必经的点数就是这两点间简单路径上的圆点的个数.那么这样问题就转化为求树上两点间经过的圆点的个数了.那么我们可以再加一个LCA来解决问题.对于两个圆点,它们的LCA一定是一个方点(当然一个是另一个的祖先时除外).经过推导可以得出 ans=(dep[u]+dep[v]-2×dep[LC…

CH#24C 逃不掉的路和 HDU3686 Traffic Real Time Query System

逃不掉的路 CH Round #24 - 三体杯 Round #1 题目描述现代社会,路是必不可少的.任意两个城镇都有路相连,而且往往不止一条.但有些路连年被各种XXOO,走着很不爽.按理说条条大路通罗马,大不了绕行其他路呗--可小撸却发现:从a城到b城不管怎么走,总有一些逃不掉的必经之路. 他想请你计算一下,a到b的所有路径中,有几条路是逃不掉的? 输入格式第一行是n和m,用空格隔开.接下来m行,每行两个整数x和y,用空格隔开,表示x城和y城之间有一条长为1的双向路.第m+2行是q.接下来…

HDU 3686 Traffic Real Time Query System (图论)

HDU 3686 Traffic Real Time Query System 题目大意给一个N个点M条边的无向图,然后有Q个询问X,Y,问第X边到第Y边必需要经过的点有多少个. solution 显然园方树+tarjan求LCA,然后求两条边之间的点必经的点的数量就是圆点的数量,然后进行分类讨论若\(LCA\)为圆点: 那么其中一个点到\(LCA\)的圆点数量为\((deep[x] - deep[lca])/2\),因为\(LCA\)为圆点被算了两遍,所以要-1 若\(LCA\)为方点:…

HDU 3686 Traffic Real Time Query System（双连通分量缩点+LCA）（2010 Asia Hangzhou Regional Contest）

Problem Description City C is really a nightmare of all drivers for its traffic jams. To solve the traffic problem, the mayor plans to build a RTQS (Real Time Query System) to monitor all traffic situations. City C is made up of N crossings and M roa…

HDU3686 Traffic Real Time Query System 题解

题目 City C is really a nightmare of all drivers for its traffic jams. To solve the traffic problem, the mayor plans to build a RTQS (Real Time Query System) to monitor all traffic situations. City C is made up of N crossings and M roads, and each road…

Traffic Real Time Query System 圆方树+LCA

题目描述 City C is really a nightmare of all drivers for its traffic jams. To solve the traffic problem, the mayor plans to build a RTQS (Real Time Query System) to monitor all traffic situations. City C is made up of N crossings and M roads, and each ro…