数学推导的博客 http://codeforces.com/contest/701/problem/D  题目 推导的思路就是 : 让每个人乘车的时间相等 ,让每个人走路的时间相等. 在图上可以这么表示 设 a 为每个人的乘车路程 ,t 为车的 1次往返的时间 ,v1是人走路的速度,v2是车速, g=n/k+(n%k==0? 0 : 1) 为这辆车需要往返的回合数 得到两个方程 : 方程1: ( 在车送第一批去然后回来接到第二批的时间 t 期间,第二批走的路程v1* t) + (车已经送达第一批…

  ~A题 A. Cards time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output There are n cards (n is even) in the deck. Each card has a positive integer written on it. n / 2 people will play new card gam…

A 第一题明显统计,注意0和long long(我WA,RE好几次) /* * Problem: A. Matrix * Author: Shun Yao */ #include <string.h> #include <stdlib.h> #include <limits.h> #include <assert.h> #include <stdio.h> #include <ctype.h> #include <math.h&…

这场是午夜场,发现学长们都睡了,改主意不打了,第二天起来打的virtual contest. A题 http://codeforces.com/problemset/problem/701/A 巨水无比,好像三四分钟就直接A了...直接n²暴力. #include <cstdio> #include <map> #include <queue> #include <cstring> #include <algorithm> #include &l…

http://codeforces.com/contest/701 A - Cards 水 // #pragma comment(linker, "/STACK:102c000000,102c000000") #include <iostream> #include <cstdio> #include <cstring> #include <sstream> #include <string> #include <alg…

题目链接:http://codeforces.com/contest/701/problem/D 题意: 给出n个学生和能载k个学生的车,速度分别为v1,v2,需要走一段旅程长为l,每个学生只能搭一次车,问最少时间到达目的地. 分析: 要使得时间最少,最后车和所有学生应该是同时到达的,我们可以观察到第一组乘车的学生和最后一组乘车的学生两者搭车时间和走路时间是相同的,那么猜想中间所有组的的学生乘车时间和走路时间是相同的(不是乘车==走路),即所有学生的乘车时间相同,走路时间相同.那么第一组学生时间…

题目链接: http://codeforces.com/contest/701/problem/C 题意: 给出一个长度为n的字符串,要我们找出最小的子字符串包含所有的不同字符. 分析: 1.尺取法,不懂得可以看今天开始学算法系列-尺取法 2.二分法,具体见代码 PS:因为讲得太少所以附上A和B的题解: A:结构体存储,将所有数sort一下,一头一尾输出即可 B:开辆个数组记录当前行或列是否有车,row[],col[],设两个变量a,b记录行列,放入一个车时,如果已标记则不用减去,否则减去(a-…

http://codeforces.com/problemset/problem/700/B 题目大意:给你一棵树,给你k个树上的点对.找到k/2个点对,使它在树上的距离最远.问,最大距离是多少? 思路:我们可以把树上的这个分成两个集合,然后两边的点的数目相等.符合这个条件的就是树的重心,所以我们只需要找到树的中心就行啦. //看看会不会爆int!数组会不会少了一维! //取物问题一定要小心先手胜利的条件 #include <bits/stdc++.h> using namespace std…

二分思想,对所要花费的时间进行二分,再以模拟的形式进行验证是否可行. 使用二分法,可以将一个求最优解的问题转化为一个判定问题,优雅的暴力. #include<cstdio> #include<iostream> #include<cstdlib> #include<cstring> #include<string> #include<algorithm> #include<map> #include<queue>…

B. Cells Not Under Attack time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Vasya has the square chessboard of size n × n and m rooks. Initially the chessboard is empty. Vasya will consequen…

Cells Not Under Attack 题意: 给出n*n的地图,有给你m个坐标,是棋子,一个棋子可以把一行一列都攻击到,在根据下面的图,就可以看出让你求阴影(即没有被攻击)的方块个数 题解: 我先是认真的看了前面之后,发现看不懂,最后一看图,就明白了,这就似乎证明了图片已经超越了语言,MD 扯远了. 这题要这么想,增加了一个点,就要减少一行一列,之后再把他们拼到一起,之后发现也就是求x*y了(x是行没有出现的个数,y是列没有出现的个数) 还有就是要注意这题是longlong,又被ll坑了…

Cards 题意: 给你n个牌,n是偶数,要你把这些牌分给n/2个人,并且让每个人的牌加起来相等. 题解: 这题我做的时候,最先想到的是模拟,之后码了一会,发现有些麻烦,就想别的方法.之后发现只要把它给的数排序就好了,排完序后输出原来的位置就好,因为每2个都能配对所以最小肯定配最大,第二小配第二大-- 之后就可以a了 代码: #include <bits/stdc++.h> using namespace std; const int INF=0x3f3f3f3f; typedef long…

A. Cards time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output There are n cards (n is even) in the deck. Each card has a positive integer written on it. n / 2 people will play new card game. At…

E. Connecting Universities time limit per test 3 seconds memory limit per test 256 megabytes input standard input output standard output Treeland is a country in which there are n towns connected by n - 1 two-way road such that it's possible to get f…

C. They Are Everywhere time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Sergei B., the young coach of Pokemons, has found the big house which consists of n flats ordered in a row from left…

 D. As Fast As Possible time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output On vacations n pupils decided to go on excursion and gather all together. They need to overcome the path with the len…

E. Connecting Universities time limit per test 3 seconds memory limit per test 256 megabytes input standard input output standard output Treeland is a country in which there are n towns connected by n - 1 two-way road such that it's possible to get f…

题目链接: C. They Are Everywhere time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Sergei B., the young coach of Pokemons, has found the big house which consists of n flats ordered in a row from…

题意:n个人要运动ll长,有个bus带其中几个人,问最短时间 最后所有人在同一时间到终点是用时最少的.由于搭bus相当于加速,每个人的加速时间应该一样.先计算bus走过的路程route.看第一个人被搭t分钟(也就是所有人以后都搭t分钟),剩余的人走t分钟,route+=v2*t.bus到了v2*t的位置,人在v1*t的位置.bus回去接人,被接的人继续前进.route2=(v2*t-v1*t)/(v1+v2)*v2(相向而行).接到人后再走v2*t,结果就是这样往复.最后一次不回头.如果要接a次…

B. Connecting Universities 大意: 给定树, 给定2*k个点, 求将2*k个点两两匹配, 每个匹配的贡献为两点的距离, 求贡献最大值 单独考虑每条边$(u,v)$的贡献即可, 最大贡献显然是左右两侧点的最小值. #include <iostream> #include <algorithm> #include <cstdio> #include <math.h> #include <set> #include <m…

一种方法是二分总时间,复杂度O(nlogn). 另外我们可以证明,当所有人同时到达终点的时候,是最优的,因为没有人的时间“浪费”了. 我们又发现,每个人的运动过程总是两段,要么是走路,要么是坐车.于是每个人的运动都是等价的(坐车的时间也相等,走路的时间也相等). 这里借用一下这个推导,懒得写了. (http://blog.csdn.net/say_c_box/article/details/52001850) 根据上面的过程得出d以后,于是有d*(组数-1)+l1=l,然后就可以解出l1,然后l…

题目链接:传送门 题目大意:n个点构成一棵树,给定 k*2 点,要分成 k 组,使每组点之间的距离之和最大. 题目思路:因为是求距离之和最大,所以我们可以知道这样一个性质.如果以一条边为界,两边的子树均有给定的点,则这条边一定会经过 min(左边的给定点数,右边的给定点数)次. 那么这条边的贡献就是经过的次数. #include <iostream> #include <cstdio> #include <cstdlib> #include <cmath>…

C. They Are Everywhere time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Sergei B., the young coach of Pokemons, has found the big house which consists of n flats ordered in a row from left…

题目大意 在n颗结点的树上有2k个需要配对的点,把他们两两配对,使得路程和最大并输出 选取一个点v lv表示v与父亲的边 那么考虑lv被经过的次数,对于一个最大的情况,lv应该为min(sv, 2*k - sv) ,其中sv是v子树中需要配对的点(包括v) 假如lv比这个值小,那么必定有a和b在v的子树外,c和d在子树内,它们分别配对 但是如果这样的话,让a和c配对,b和d配对,显然更优 所以lv只能等于min(sv, 2*k - sv) 最后输出所有点的这个值的和即可 #include <io…

Description There are n cards (n is even) in the deck. Each card has a positive integer written on it. n / 2 people will play new card game. At the beginning of the game each player gets two cards, each card is given to exactly one player. Find the w…

Description Sergei B., the young coach of Pokemons, has found the big house which consists of n flats ordered in a row from left to right. It is possible to enter each flat from the street. It is possible to go out from each flat. Also, each flat is…

Description Vasya has the square chessboard of size n × n and m rooks. Initially the chessboard is empty. Vasya will consequently put the rooks on the board one after another. The cell of the field is under rook's attack, if there is at least one roo…

D. As Fast As Possible time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output On vacations n pupils decided to go on excursion and gather all together. They need to overcome the path with the leng…

C. They Are Everywhere time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Sergei B., the young coach of Pokemons, has found the big house which consists of n flats ordered in a row from left…

B. Cells Not Under Attack time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Vasya has the square chessboard of size n × n and m rooks. Initially the chessboard is empty. Vasya will consequen…