Sorting is often useful as the first step in many different tasks. The most common task is to make finding things easier, but there are other uses also. Challenge Given a list of unsorted numbers, can you find the numbers that have the smallest absol…

Numeros, The Artist, had two lists A and B, such that, B was a permutation of A. Numeros was very proud of these lists. Unfortunately, while transporting them from one exhibition to another, some numbers from List A got left out. Can you find out the…

[HDU3117]Fibonacci Numbers 题面 求斐波那契数列的第\(n\)项的前四位及后四位. 其中\(0\leq n<2^{32}\) 题解 前置知识:线性常系数齐次递推 其实后四位还是比较好求,矩阵快速幂就可以了,主要是前四位. 先用线性常系数齐次递推求出斐波那契数列的通项公式 \[ f_n=\frac{\sqrt 5}{5}\left((\frac{1+\sqrt5}{2})^n-(\frac{1-\sqrt5}{2})^n\right) \] 因为数列的前\(39\)项我们…

[CF55D]Beautiful numbers(动态规划) 题面 洛谷 CF 题解 数位\(dp\) 如果当前数能够被它所有数位整除,意味着它能够被所有数位的\(lcm\)整除. 所以\(dp\)的时候前面所有数的\(lcm\)要压进\(dp\)值中. 又因为\(lcm\)的余数也是有意义的,但是又不能暴力记, 所以记录一下\([1,9]\)所有数的\(lcm\)也就是\(2520\)就好了. 但是数组太大,实际上,有意义的\(lcm\)个数只有不到\(50\)个,重新编号就可以压缩状态了.…

[CF628D]Magic Numbers 题意:求[a,b]中,偶数位的数字都是d,其余为数字都不是d,且能被m整除的数的个数(这里的偶数位是的是从高位往低位数的偶数位).$a,b<10^{2000},m \le 2000 ,0 \le d \le 9$ 题解:用f[i][j]表示有i+1位,第i位是d,且%m=j的数的个数.(这个状态可能有点奇怪,不过比较便于转移)然后转移方式还是惯用的方法,判一下如果原数的偶数位不是d或者奇数位是d则停止计算即可. 对了,题意有bug.题里说个位数的偶数位…

[CF55D]Beautiful numbers 题面 洛谷 题解 考虑到如果一个数整除所有数那么可以整除他们的\(lcm\),而如果数\(x\)满足\(x\bmod Lcm(1,2...,9)=r\),且\(r\bmod Lcm\{x有的数\}=0\),那么这个数一定满足条件. 因为\(Lcm(1,2...,9)=2520\)比较小,所以我们可以存下来. 考虑数位dp,我们设\(f[i][lcm][r]\)表示目前\(dp\)到第\(i\)位,当前已选的数的\(lcm\)为\(lcm\),前面…

Description Write a program that takes as input a rooted tree and a list of pairs of vertices. For each pair (u,v) the program determines the closest common ancestor of u and v in the tree. The closest common ancestor of two nodes u and v is the node…

题目链接:Running Time of Quicksort Challenge In practice, how much faster is Quicksort (in-place) than Insertion Sort? Compare the running time of the two algorithms by counting how many swaps or shifts each one takes to sort an array, and output the dif…

https://www.hackerrank.com/challenges/how-many-substrings/problem 题解 似乎是被毒瘤澜澜放弃做T3的一道题(因为ASDFZ有很多人做过,当然,他换了一道更毒瘤的--) 仓鼠在最后一天的时候提了一嘴然后我发现依旧菜菜的不会--(因为太菜模拟天天被吊打) 仓鼠好神仙啊%%%(烤熟了味道怎么样啊) 这道题三个数据结构结合在一起使用,但是感觉却没有那么码农,就是直接把板子套一套(当然板子不熟另当别论),用namespace的话可以降低编码…

In the Quicksort challenges, you sorted an entire array. Sometimes, you just need specific information about a list of numbers, and doing a full sort would be unnecessary. Can you figure out a way to use your partition code to find the median in an a…