那个人第一步肯定要么能向下走,要么能向右走.于是一定可以判断出上下是否对调,或者左右是否对调. 然后他往这个方向再走一走就能发现一定可以再往旁边走,此时就可以判断出另一个方向是否对调. 都判断出来以后,跑个spfa或者bfs就行了. 细节较多……有一些边界情况需要处理.比如终点在第一行或者第一列的情况. #include<cstdio> #include<queue> #include<cstring> #include<algorithm> using n…

地址:http://codeforces.com/contest/811/problem/D 题目: D. Vladik and Favorite Game time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output This is an interactive problem. Vladik has favorite game, in…

http://codeforces.com/contest/811/problem/C 题意: 给出一行序列,现在要选出一些区间来(不必全部选完),但是相同的数必须出现在同一个区间中,也就是说该数要么不选,选了就必须出现在同一个区间,最后累加区间不同的数的异或值. 思路: 先预处理,求出每个数的左位置和右位置. d[i]表示分析到第 i 位时的最大值. #include<iostream> #include<algorithm> #include<cstring> #i…

B. Vladik and Complicated Book time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Vladik had started reading a complicated book about algorithms containing n pages. To improve understanding o…

划分那个序列,没必要完全覆盖原序列.对于划分出来的每个序列,对于某个值v,要么全都在该序列,要么全都不在该序列.  一个序列的价值是所有不同的值的异或和.整个的价值是所有划分出来的序列的价值之和.    求整个的价值的最大值   f(i)表示最后一个划分序列的右端点为i时,1~i的答案. f(i)=max{max{f(j)}(1<=j<i)+xorsum(j+1,i)(j+1到i的区间合法)}(1<=i<=n) 需要在转移的时候,顺便处理f(i)的前缀max. 最终的答案就是所有f…

A. Vladik and Courtesy time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output At regular competition Vladik and Valera won a and b candies respectively. Vladik offered 1 his candy to Valera. Afte…

题目传送门 /* 题意:告诉起点终点,踩一次, '.'变成'X',再踩一次,冰块破碎,问是否能使终点冰破碎 DFS:如题解所说,分三种情况:1. 如果两点重合,只要往外走一步再走回来就行了:2. 若两点相邻, 那么要不就是踩一脚就破了或者踩一脚走开再走回来踩一脚破了:3. 普通的搜索看是否能到达, 若能还是要讨论终点踩几脚的问题:) DFS 耗时大,险些超时,可以用BFS来做 */ #include <cstdio> #include <algorithm> #include &l…

题目传送门 /* 题意:问最少替换'*'为'.',使得'.'连通的都是矩形 BFS:搜索想法很奇妙,先把'.'的入队,然后对于每个'.'八个方向寻找 在2*2的方格里,若只有一个是'*',那么它一定要被替换掉 */ #include <cstdio> #include <iostream> #include <algorithm> #include <cstring> #include <queue> using namespace std; ;…

A. Vladik and Courtesy 题面 At regular competition Vladik and Valera won a and b candies respectively. Vladik offered 1 his candy to Valera. After that Valera gave Vladik 2 his candies, so that no one thought that he was less generous. Vladik for same…

A. Vladik and Courtesy 2 seconds 256 megabytes   At regular competition Vladik and Valera won a and b candies respectively. Vladik offered 1 his candy to Valera. After that Valera gave Vladik 2 his candies, so that no one thought that he was less gen…