Firt thought: an variation to LCS problem - but this one has many tricky detail. I learnt the solution from this link:https://github.com/wangyongliang/Algorithm/blob/master/hackerrank/Strings/Square%20Subsequences/main.cc And here is his code with my…

https://www.hackerrank.com/contests/w6/challenges/consecutive-subsequences 求数组中被k整除的子段和有几个.这个要利用sum[i..j] = sum[j] - sum[i-1],注意这样还要保留一个sum[-1]=0(根据下标的起点怎么定).那么能被k整除的子段sum[i..j]的sum[j]和sum[i-1] %k的值是一样的. #include <iostream> #include <vector> u…

乱听课记录 关于树的分治问题&杂题选讲 张哲宇 边分治 (边分不是很鸡肋吗) 例题一 题目大意:给出两颗有正负边权的树,求出两个点\(u,v​\)使得两棵树中\((u,v)​\)距离的和最大.\(n \le 10^5​\). 点分治 例题二 题目大意:\(n\)个点的树,每个点有非负点权,求权值第\(k\)大的联通块.\(n,k \le 10^5\). 考虑点分治,对于每一个分治中心,进行的点分相当于多了一个"强制选该分治中心"的限制. 对于每一层的分治,我们dfs重标号,那么…

原题地址 对于给定的两个约束条件,可以通过联立方程组直接解出子序列A的和和子序列B的和,即sum(A) = (r + s) / 2,sum(B) = (r - s) / 2,假设|A|=|B|=n 所以问题变成了,在一个数组中求长度为n且子序列和为sum(A)或sum(B)有多少个. 假设count(n, s)表示长度为n且子序列和为s有多少个,则要求的是count(n, sum(A)) * count(n, sum(B)),其中1<=n<=m 或者通俗来说就是m个k-sum问题 求k-sum…

Back to Square 1 题目连接: https://www.hackerrank.com/contests/ieeextreme-challenges/challenges/back-to-square-1 Description The game "Back to Square 1" is played on a board that has n squares in a row and n-1 probabilities. Players take turns playi…

Xtreme8.0 - Magic Square 题目连接: https://www.hackerrank.com/contests/ieeextreme-challenges/challenges/magic-square Description Johnny designed a magic square (square of numbers with the same sum for all rows, columns and diagonals i.e. both the main di…

题目链接: C. Subsequences time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output For the given sequence with n different elements find the number of increasing subsequences with k + 1 elements. It is…

Remember the story of Little Match Girl? By now, you know exactly what matchsticks the little match girl has, please find out a way you can make one square by using up all those matchsticks. You should not break any stick, but you can link them up, a…

Given a sequence of words, check whether it forms a valid word square. A sequence of words forms a valid word square if the kth row and column read the exact same string, where 0 ≤k < max(numRows, numColumns). Note: The number of words given is at le…

Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built-in library function such as sqrt. Example 1: Input: 16 Returns: True Example 2: Input: 14 Returns: False Credits:Speci…