题目大意: n个点,第i个点和第i+1个点可以构成向量,问最少删除多少个点可以让构成的向量顺时针旋转或者逆时针旋转. 分析: dp很好想,dp[j][i]表示以向量ji(第j个点到第i个点构成的向量)为终点的最大顺时针/逆时针向量数.状态转移方程为 dp[j][i] = max{dp[k][j]+1}. 问题个关键是如何判断2个向量是顺时针还是逆时针. 计算几何用的知识是求叉积和点积,叉积的作用是判断两个向量的左右(顺逆),点积的作用是判断两个向量的前后.举个例子,假设有2个向量v1,v2,‘*…

先看看上一个题: 题目大意是: 矩阵中有N个被标记的元素,然后针对每一个被标记的元素e(x,y),你要在所有被标记的元素中找到一个元素E(X,Y),使得X>x并且Y>y,如果存在多个满足条件的元素,先比较X,选择X最小的那个,如果还是有很多满足条件的元素,再比较Y,选择Y最小的元素,如果不存在就输出两个-1: 分析: 直接暴力就行了 这个题目大意: 这个题是上个题的坚强版,每次会增加或减少一个点,仍然找到一个元素E(X,Y),使得X>x并且Y>y: 最多有200000次操作,每次只…

题意 : 找联通块的个数,Saya定义两个相连是 |xa-xb| + |ya-yb| ≤ 1 ,但是Kudo定义的相连是 |xa-xb|≤1 并且 |ya-yb|≤1.输出按照两种方式数的联通块的各数. 思路 : 按照第一种定义方式就只能是上下左右四个位置,而第二种则是周围那8个都是相连的. #include <iostream> #include <stdio.h> #include <stdlib.h> #include <queue> #include…

Hello World! Time Limit: 1000MS Memory limit: 65536K 题目描述 We know that Ivan gives Saya three problems to solve (Problem F), and this is the first problem. "We need a programmer to help us for some projects. If you show us that you or one of your frie…

Phone Number Time Limit: 1000MS Memory limit: 65536K 题目描述 We know that if a phone number A is another phone number B's prefix, B is not able to be called. For an example, A is 123 while B is 12345, after pressing 123, we call A, and not able to call…

Identifiers Time Limit: 1000MS Memory limit: 65536K 题目:http://acm.sdut.edu.cn/sdutoj/problem.php?action=showproblem&problemid=2163 题目描写叙述  Identifier is an important concept in the C programming language. Identifiers provide names for several languag…

Mountain Subsequences 题目描述 Coco is a beautiful ACMer girl living in a very beautiful mountain. There are many trees and flowers on the mountain, and there are many animals and birds also. Coco like the mountain so much that she now name some letter s…

n a^o7 ! 题目:http://acm.sdut.edu.cn/sdutoj/problem.php?action=showproblem&problemid=2413 Time Limit: 1000MS Memory limit: 65536K 题目描写叙述 All brave and intelligent fighters, next you will step into a distinctive battleground which is full of sweet and h…

http://acm.sdut.edu.cn/sdutoj/problem.php?action=showproblem&problemid=2877 题目描述 The problems called "Angry Birds" and "Angry Birds Again and Again" has been solved by many teams in the series of contest in 2011 Multi-University Tr…

Mine Number 题目:http://acm.sdut.edu.cn/sdutoj/problem.php? action=showproblem&problemid=2410 Time Limit: 1000ms Memory limit: 65536K 有疑问?点这里^_^ 题目描写叙述 Every one once played the game called Mine Sweeping, here I change the rule. You are given an n*m ma…