[contest 781] 9.6 - XJOI czx的温暖题... T1 军训…

题目链接:http://codeforces.com/contest/781/problem/D ${F[i][j][k][0,1]}$表示是否存在从${i-->j}$的路径走了${2^{k}}$步,${0,1}$表示第$1$步是走路还是骑车的. 倍增$Floyed$转移即可. 但是复杂度不对,考虑这个状态是记录的$bool$类型,将状态(${j}$)压一下位(可以用${bitset}$). #include<iostream> #include<cstdio> #inclu…

题目链接:http://codeforces.com/contest/781/problem/B 去tmd 2-SAT 直接贪心就可以过去了,优先选择第二种情况. 然而....可以被叉掉(数据水了) ABC DDD ABD DOG #include<iostream> #include<cstdio> #include<algorithm> #include<vector> #include<cstdlib> #include<cmath&…

ps:最近碰到一些用bitset优化常数的题目,以前也有接触但是都没有记下来,所以来写一篇博文 记录以后碰到的类似的题目. 应用一: 优化boolean multiplication 在做dp的时候,有时候会需要将两个dp矩阵相乘,且矩阵的元素都是bool型. 计算矩阵A*B=C     C[i,j]=1 当且仅当存在k,A[i,k]=1 && B[k][j]=1 . 直接算需要O(n3)的时间.可以用bitset 优化常数. 做法如下: bitset<N> A[N],B[N]…

1. 判断一个数是否是2的方幂n > 0 && ((n & (n - 1)) == 0 ) 解释((n & (n-1)) == 0): 如果A&B==0,表示A与B的二进制形式没有在同一个位置都为1的时候. 那么本题到底啥意思?? 不妨先看下n-1是什么意思. 令:n=1101011000(二进制,十进制也一样),则 n-1=1101010111. n&(n-1)=1101010000 由此可以得出,n和n-1的低位不一样,直到有个转折点,就是借位的那…

5/12 2016 Multi-University Training Contest 6 官方题解 打表找规律/推公式 A A Boring Question(BH) 题意: ,意思就是在[0,n]里选择m个数字的相邻数字二项式组合的积的总和. 思路: 想了好久,不会,但是这题有300多人过,怀疑人生... 打了个表: n=0, m=2, ans=1n=1, m=2, ans=3n=2, m=2, ans=7n=3, m=2, ans=15n=4, m=2, ans=31n=5, m=2, a…

    Programming Contest Problem Types Hal Burch conducted an analysis over spring break of 1999 and made an amazing discovery: there are only 16 types of programming contest problems! Furthermore, the top several comprise almost 80% of the problems s…

Area of Mushroom Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 2390    Accepted Submission(s): 578 Problem Description Teacher Mai has a kingdom with the infinite area. He has n students guard…

Differencia Time Limit: 10000/10000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 601    Accepted Submission(s): 173 Problem Description Professor Zhang has two sequences a1,a2,...,an and b1,b2,...,bn. He wants to…

Rigid Frameworks Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 337    Accepted Submission(s): 273 Problem Description Erik Demaine is a Professor in Computer Science at the Massachusetts Insti…