题意 给定一张无向图,对每个点$i\in S$求$\min_{j\in S} {2\times d(i,j)+a_j}$ 考虑多源多汇最短路会超时,换个角度考虑每个$j$,如果$j=i$,那么答案为$a_i$,如果有更优的方案,那么为$i$到$j$的一条路径加上$a_j$,将这个过程看成两条路径,并且将$a_j$独立为一条路径,就得到最短路算法中的松弛操作,可以建立一个超级源点,连向各点,边权为$a_i$,那么从源点跑一遍最短路之后就是每个点所求答案 时间复杂度$O(n\log n)$ 代码 #…

D. Buy a Ticket 分析 建一个源点,连向所有结点,边的花费为那个结点的花费,图中原有的边花费翻倍,最后跑一遍最短路即可. code #include<bits/stdc++.h> using namespace std; const int N = 2e5 + 10; const long long INF = 2e18; struct Edge { int to; long long w; }; vector<Edge> G[N]; long long d[N];…

这场打了小号 A. Word Correction time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output Victor tries to write his own text editor, with word correction included. However, the rules of word correction are…

[比赛链接] 点击打开链接 [题解] Problem A Word Correction[字符串] 不用多说了吧,字符串的基本操作 Problem B  Run for your prize[贪心] 我们可以将这个数轴一分为二,小于等于500000的由第一个人领,否则由第二个人领 Problem C Constructing tests[贪心][数学] 首先我们发现 : N^2 - (N / M)^2 = x (N/M向下取整) 然后我们算出N的上下界,发现: sqrt(x+1)<=N<=sq…

http://codeforces.com/contest/938 A:sb题 //#pragma comment(linker, "/stack:200000000") //#pragma GCC optimize("Ofast,no-stack-protector") //#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native") //#pragm…

C. Constructing Tests time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output Let's denote a m-free matrix as a binary (that is, consisting of only 1's and 0's) matrix such that every square submat…

链接:http://codeforces.com/contest/665/problem/E 题意:求规模为1e6数组中,连续子串xor值大于等于k值的子串数: 思路:xor为和模2的性质,所以先预处理之后,可以枚举这种确实子串区间的方法为O(n^2): 优化?把每一个前缀xor扔到二叉树中,从根节点出发,以高位前缀值的二进制数构造一颗二叉树,这样就可以在构造的时候,实现对子树节点个数的求解:之后在线求解到当前节点的可选的前缀xor的个数, 即以k为主线 如果当前位k为1,则在前缀二叉树中只能找…

Educational Codeforces Round 41 (Rated for Div. 2) E. Tufurama (CDQ分治 求 二维点数) time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output One day Polycarp decided to rewatch his absolute favourite epi…

[Educational Codeforces Round 16]E. Generate a String 试题描述 zscoder wants to generate an input file for some programming competition problem. His input is a string consisting of n letters 'a'. He is too lazy to write a generator so he will manually ge…

[Educational Codeforces Round 16]D. Two Arithmetic Progressions 试题描述 You are given two arithmetic progressions: a1k + b1 and a2l + b2. Find the number of integers x such that L ≤ x ≤ R andx = a1k' + b1 = a2l' + b2, for some integers k', l' ≥ 0. 输入 Th…