Tetrahedron time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given a tetrahedron. Let's mark its vertices with letters A, B, C and D correspondingly. An ant is standing in the verte…

Codeforces Round #113 (Div. 2) B. Polygons 题意 给一个\(N(N \le 10^5)\)个点的凸包 \(M(M \le 2 \cdot 10^4)\)次询问,每次给一个点判断该点是否在凸包内. 思路 按\(y\)坐标将凸包分成两部分. 在左右两边二分找出夹住该点的\(y\)值区间,判断叉积正负. 代码 B. Polygons D. Shoe Store 题意 有\(N \le 10^5\)双鞋,每双鞋价格为\(c_i \le 10^9\),大小为\(s…

题目链接: https://codeforces.com/contest/166/problem/E 题目: 题意: 给你一个三菱锥,初始时你在D点,然后你每次可以往相邻的顶点移动,问你第n步回到D点的方案数. 思路: 打表找规律得到的序列是0,3,6,21,60,183,546,1641,4920,14763,通过肉眼看或者oeis可以得到规律为. dp计数:dp[i][j]表示在第i步时站在位置j的方案数,j的取值为[0,3],分别表示D,A,B,C点,转移方程肯定是从其他三个点转移. 代码…

题目链接: http://codeforces.com/problemset/problem/213/B B. Numbers time limit per test 2 secondsmemory limit per test 256 megabytes 问题描述 Furik loves writing all sorts of problems, especially such that he can't solve himself. You've got one of his proble…

题目链接: http://codeforces.com/problemset/problem/214/B Hometask time limit per test:2 secondsmemory limit per test:256 megabytes 问题描述 Furik loves math lessons very much, so he doesn't attend them, unlike Rubik. But now Furik wants to get a good mark fo…

D. Kindergarten Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/problemset/problem/484/D Description In a kindergarten, the children are being divided into groups. The teacher put the children in a line and associated each child wi…

A. Boredom Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/contest/455/problem/A Description Alex doesn't like boredom. That's why whenever he gets bored, he comes up with games. One long winter evening he came up with a game and d…

题目链接:https://codeforces.com/contest/1105 C. Ayoub and Lost Array 题目大意:一个长度为n的数组,数组的元素都在[L,R]之间,并且数组全部元素的和可以被3整除,问有多少种方法构建出该数组.答案模1000000007 例 输入 2 1 3 输出 3 note:满足的情况只有[1,2],[2,1],[3,3] 解题思路:用dp[i][j]表示长度为i的数组,元素大小在[L,R]之间,并且元素和模3的余数为j的方案数,我们可以计算出[L,…

https://codeforces.com/contest/1113/problem/C 题意 一个n个数字的数组a[],求有多少对l,r满足\(sum[l,mid]=sum[mid+1,r]\),sum为异或和(n<=3e5,a[i]<=2^20) 题解 异或和为零的区间可以分成任意两个区间(这两个区间的异或和相等) 定义dp[i][j]为异或和为i,下标为j(只记录奇偶)的前缀个数 枚举r,然后累加l 代码 #include<bits/stdc++.h> #define M…

C. Journey 题目连接: http://codeforces.com/contest/721/problem/C Description Recently Irina arrived to one of the most famous cities of Berland - the Berlatov city. There are n showplaces in the city, numbered from 1 to n, and some of them are connected…