题目链接: 题目 D. Kay and Snowflake time limit per test 3 seconds memory limit per test 256 megabytes input standard input output standard output 问题描述 After the piece of a devilish mirror hit the Kay's eye, he is no longer interested in the beauty of the r…

D. Kay and Snowflake     After the piece of a devilish mirror hit the Kay's eye, he is no longer interested in the beauty of the roses. Now he likes to watch snowflakes. Once upon a time, he found a huge snowflake that has a form of the tree (connect…

B. Kay and Snowflake 题目连接: http://www.codeforces.com/contest/685/problem/B Description After the piece of a devilish mirror hit the Kay's eye, he is no longer interested in the beauty of the roses. Now he likes to watch snowflakes. Once upon a time,…

D - Kay and Snowflake 题目大意:给你一棵数q个询问,每个询问给你一个顶点编号,要你求以这个点为根的子树的重心是哪个节点. 定义:一棵树的顶点数为n,将重心去掉了以后所有子树的顶点的个数的两倍不会超过n. 性质 1 :树中所有点到某个点的距离和中,到重心的距离和是最小的,如果有两个距离和,他们的距离和一样. 性质 2 :把两棵树通过某一点相连得到一颗新的树,新的树的重心必然在连接原来两棵树重心的路径上. 性质 3 :一棵树添加或者删除一个节点,树的重心最多只移动一条边的位置.…

A http://codeforces.com/contest/685/standings 题意:给你n和m,找出(a,b)的对数,其中a满足要求:0<=a<n,a的7进制的位数和n-1的7进制的位数相同,b满足要求:0<=b<m,b的7进制的位数和m-1的7进制的位数相同,且a和b的7进制下的位上的数都不相同 思路:如果a b的位数和大于7显然会有重复,缩小范围以后,可以根据题意暴力枚举 // #pragma comment(linker, "/STACK:102400…

链接: https://codeforces.com/contest/1263/problem/E 题意: The development of a text editor is a hard problem. You need to implement an extra module for brackets coloring in text. Your editor consists of a line with infinite length and cursor, which point…

http://codeforces.com/contest/686/problem/D 给出q个询问,每次要求询问以x为根的子树中,哪一个点是重心. 树的重心:求以cur为根的子树的重心,就是要找一个点,使得删除这个点后,分开来的零散的子树中,节点数的最大值最小.并且最大值最多也只是son[cur] / 2,因为最坏情况(最难分)也就是一条直线,选中间点就可以了. 例如 询问1的时候,就应该删除3,然后得到4个零散分支,2个大小是1,2个是2. 算法思路: 直观来说,应该是删除那个儿子数最多的那…

A. Free Ice Cream 题目连接: http://www.codeforces.com/contest/686/problem/A Description After their adventure with the magic mirror Kay and Gerda have returned home and sometimes give free ice cream to kids in the summer. At the start of the day they hav…

C. Robbers' watch time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Robbers, who attacked the Gerda's cab, are very successful in covering from the kingdom police. To make the goal of catchi…

题目链接:http://codeforces.com/problemset/problem/686/C 给你n和m,问你有多少对(a, b) 满足0<=a <n 且 0 <=b < m 且a的7进制和n-1的7进制位数相同 且b的7进制和m-1的7进制位数相同,还有a和b的7进制上的每位上的数各不相同. 看懂题目,就很简单了,先判断a和b的7进制位数是否超过7,不超过的话就dfs暴力枚举计算就可以了. //#pragma comment(linker, "/STACK:1…