题意:输入一棵树,输出前k小的点对最短距离dis(i,j)的和. 模拟,官方题解说得很清楚了.不重复了. http://bestcoder.hdu.edu.cn/ 需要注意的是,复杂度要O(n+k),不能用set,map之类的标记是否访问. 一开始TLE了,去掉标记后wa了.最后发现对队列的元素加个前缀,就可以了,即标记该条边是从哪个点延伸的. #include <cstdio> #include <cstring> #include <iostream> #inclu…

http://acm.hdu.edu.cn/showproblem.php?pid=5102 给一棵树,求出所有节点的距离中前k小的路径长度和 由于路径长度的定义为两点之间的边的个数,所有遍历1~n-1条边组成的路径,暴力擦线过,3000+ms #include <cstdio> #include <cstdlib> #include <cmath> #include <cstring> #include <string> #include &l…

题目链接: http://acm.hdu.edu.cn/showproblem.php?pid=5122 Problem Description Matt's friend K.Bro is an ACMer.Yesterday, K.Bro learnt an algorithm: Bubble sort. Bubble sort will compare each pair of adjacent items and swap them if they are in the wrong or…

题意:给你n-1条边,然后没两个节点的距离按照递增的顺序,求出前k项的和. 官方题解: 把所有边(u,v) 以及(v,u)放入一个队列,队列每弹出一个元素(u,v),对于所有与u相邻的点w,如果w!=v,就把(w,u)入队.这样就能一个一个生成前K小的距离. 注意到每条边实际上会入队两次,只要把K翻倍且把ans除2即可,时间复杂度为O(n+K): 这里只是实现一下而已. 代码: #pragma comment(linker, "/STACK:1024000000,1024000000"…

题意: N个点的一棵树.定义点u和点v的距离等于它们之间的路径(唯一的)的长度.这样我们可以得到n*(n-1)/2个距离. 将它们从小到大排序,问前K个数的和是多少. 思路: 将边长为1的树枝都入队列.每次取出一个,然后从这根树枝的前端生出一个新点,变成距离加1的一根新树枝,将其入队列.如此操作下去. 可得到所有的各种长度的树枝.因为每根树枝其实有两个在队列里(互为反方向生长),故求前2*K个数的和,然后除以2. *:我们取前队列里的前2K个,就算后面的若干些不是一对一对的,也一定可以取2K个以…

Dying Light Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)Total Submission(s): 513    Accepted Submission(s): 122 Problem Description LsF is visiting a local amusement park with his friends, and a mirror room su…

异或密码 Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others) Problem Description 晨晨在纸上写了一个长度为N的非负整数序列{ai}.对于这个序列的一个连续子序列{al,al+1,-,ar}晨晨可以求出其中所有数异或的结果 alxoral+1xor...xorar其 中xor表示位异或运算,对应C.C++. Java等语言中的^运算.小璐提出了M个询问,每个询问用…

Relative atomic mass Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others) Total Submission(s): 66    Accepted Submission(s): 59 Problem Description Relative atomic mass is a dimensionless physical quantity, the ratio of…

Basic Data Structure Time Limit: 7000/3500 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 872    Accepted Submission(s): 236 Problem Description Mr. Frog learned a basic data structure recently, which is called stac…

Minimum's Revenge Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 283    Accepted Submission(s): 219 Problem Description There is a graph of n vertices which are indexed from 1 to n. For any pai…