P2864 [USACO06JAN]树林The Grove 神奇的射线法+bfs 裸的bfs很难写....... 那么我们找一个最外围障碍点,向图的外边引一条虚拟射线. 蓝后bfs时经过这条射线奇数次最后又回到起点的,就是满足条件的路径 最后来个bfs+记忆化 #include<iostream> #include<cstdio> #include<cstring> #include<queue> using namespace std; #define N…

P2864 [USACO06JAN]树林The Grove(bfs) 题面 题目描述 The pasture contains a small, contiguous grove of trees that has no 'holes' in the middle of the it. Bessie wonders: how far is it to walk around that grove and get back to my starting position? She's just s…

树木(grove)Time Limit: 1Sec Memory Limit: 64 MB[Description]牧场里有一片树林,林子里没有坑．贝茜很想知道,最少需要多少步能围绕树林走一圈,最后回到起点．她能上下左右走,也能走对角线格子．牧场被分成R 行C 列(1≤R≤50,1≤C≤50)．下面是一张样例的地图,其中“．”表示贝茜可以走的空地, “X”表示树林, “*”表示起点．而贝茜走的最近的路已经特别地用“+”表示出来． ...+.....+X+...+XXX+...+XXX+..+X.…

1656: [Usaco2006 Jan] The Grove 树木 Time Limit: 5 Sec  Memory Limit: 64 MBSubmit: 186  Solved: 118[Submit][Status][Discuss] Description The pasture contains a small, contiguous grove of trees that has no 'holes' in the middle of the it. Bessie wonders…

Description The pasture contains a small, contiguous grove of trees that has no 'holes' in the middle of the it. Bessie wonders: how far is it to walk around that grove and get back to my starting position? She's just sure there is a way to do it by…

题目描述 现在有一片树林,小B很想知道,最少需要多少步能围绕树林走一圈,最后回到起点．他能上下左右走,也能走对角线格子. 土地被分成RR行CC列1≤R≤50,1≤C≤501≤R≤50,1≤C≤50,下面是一张样例的地图,其中“.”表示小B可以走的空地,"X"表示树林,"*”表示起点.而小B走的最近的路己经特别地用“+”表示出来. ....... ...X... ..XXX.. ...XXX. ...X... ......* 题目保证,一定有合法解并且有且只有一片树林,树林一定…

http://www.lydsy.com/JudgeOnline/problem.php?id=1656 神bfs! 我们知道,我们要绕这个联通的树林一圈. 那么,我们想,怎么才能让我们的bfs绕一个圈做bfs呢 我们可以这样:从联通的任意边界点引一条交边界的射线. 为什么呢?因为这样当我们的bfs到这条射线时,我们可以不向射线拓展! 可是我们考虑的是绕一个圈,那么我们要考虑从另一个放向到达射线的情况(即饶了一圈后到射线我们要考虑拓展) 这样我们就能保证绕了联通块一圈,然后是最短距离 具体细节看…

The Grove Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 904   Accepted: 444 Description The pasture contains a small, contiguous grove of trees that has no 'holes' in the middle of the it. Bessie wonders: how far is it to walk around t…

The Grove Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 641   Accepted: 297 Description The pasture contains a small, contiguous grove of trees that has no 'holes' in the middle of the it. Bessie wonders: how far is it to walk around t…

Luogu2860 [USACO06JAN]冗余路径Redundant Paths 给定一个连通无向图,求至少加多少条边才能使得原图变为边双连通分量 \(1\leq n\leq5000,\ n-1\leq m\leq10^4\) tarjan 边双无疑不用考虑,于是就可以边双缩点成一棵树 令现在要连的边为 \((u,\ v)\) ,当前树上 \(bl_u\) 到 \(bl_v\) 的链将会变为一个新的点双,可以将他们看为一个新的点 可以贪心地连边使得每次连边后,不复存在的点尽量多,当只剩一个点时…