题目链接: Connections between cities Time Limit: 10000/5000 MS (Java/Others)     Memory Limit: 32768/32768 K (Java/Others) Problem Description   After World War X, a lot of cities have been seriously damaged, and we need to rebuild those cities. However,…

思路:LCA裸题.本来是帮pechpo调错,结果自己写了半天… 设$dis_x$是点$x$到根结点距离,不难想到两点$u$.$v$之间最短距离等于$dis_u+dis_v-dis_{LCA(u,v)}\times 2$. 然后我们可以用Tarjan做,然后发现MLE了. 以为是这题卡vector的内存,于是改成了链式前向星,还是MLE. 后来发现题目的内存限制只有32M,算了算,如果将数据离线保存下来,大约有20000K左右,再加上函数里面的栈,似乎确实有点危险. 最后改成用ST做,只用了585…

题意:n棵树,求任意两点的最短距离. 解题关键:并查集判断两点是否位于一棵树上,然后求最短距离即可.此题可以直接对全部区间直接进行st表,因为first数组会将连接的两点的区间表示出来. //#pragma comment(linker, "/STACK:1024000000,1024000000") #include<cstdio> #include<cstring> #include<algorithm> #include<cstdlib&…

第一次按常规的方法求,将所有的查询的u,v,和最近公共祖先都保存起来,然后用tarjan+并查集求最近公共祖先.因为询问的次数过多,所以在保存查询的时候总是MLE,后来参考了一下别人的代码,才突然觉悟,可以先将u,v,和其最近公共祖先保存到数组,然后再求结果,为什么不能直接保存其结果了.如果只保存结果的话,保存查询操作就可以节约1/3的内存,所以基本可以过了. 代码如下: 方法一: #include <iostream> #include <cstdio> #include <…

Connections between cities Time Limit: 10000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 4425    Accepted Submission(s): 1263 Problem Description After World War X, a lot of cities have been seriously damag…

Connections between cities Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 896 Accepted Submission(s): 236   Problem Description After World War X, a lot of cities have been seriously damaged, an…

Connections between cities [题目链接]Connections between cities [题目类型]LCA Tarjan &题意: 输入一个森林,总节点不超过N(N<10000),由C次询问(C<1000000),每次询问两个点,如果来联通输出,两点之间的距离,如果不来联通,输出"Not connected" &题解: md,就没人吐槽这题询问时有相等的情况吗?我被这个坑了一天= = 最后把ans数组置为-1才过的,以前一直初…

Connections between cities Time Limit: 10000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Problem Description After World War X, a lot of cities have been seriously damaged, and we need to rebuild those cities. However, some mat…

Connections between cities Time Limit: 10000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 11964    Accepted Submission(s): 2786 Problem Description After World War X, a lot of cities have been seriously damag…

Connections between cities Time Limit: 10000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 4057    Accepted Submission(s): 1178 Problem Description After World War X, a lot of cities have been seriously damage…