onlyblues

摘要： Count Beautiful Substrings II You are given a string s and a positive integer k. Let vowels and consonants be the number of vowels and consonants in a 阅读全文

摘要： Make Lexicographically Smallest Array by Swapping Elements You are given a 0-indexed array of positive integers nums and a positive integer limit. In 阅读全文

摘要： D. Small GCD Let $a$, $b$, and $c$ be integers. We define function $f(a, b, c)$ as follows: Order the numbers $a$, $b$, $c$ in such a way that $a \le 阅读全文

摘要： D. Ones and Twos You are given a $1$-indexed array $a$ of length $n$ where each element is $1$ or $2$. Process $q$ queries of the following two types: 阅读全文

摘要： D. Letter Picking Alice and Bob are playing a game. Initially, they are given a non-empty string $s$, consisting of lowercase Latin letters. The lengt 阅读全文

摘要： 【模板】可持久化线段树 2 题目背景 这是个非常经典的可持久化权值线段树入门题——静态区间第 $k$ 小。 数据已经过加强，请使用可持久化权值线段树。同时请注意常数优化。 题目描述 如题，给定 $n$ 个整数构成的序列 $a$，将对于指定的闭区间 $[l, r]$ 查询其区间内的第 $k$ 小值。 阅读全文

摘要： F. A Growing Tree You are given a rooted tree with the root at vertex $1$, initially consisting of a single vertex. Each vertex has a numerical value, 阅读全文

摘要： D. Absolute Beauty Kirill has two integer arrays $a_1,a_2,\ldots,a_n$ and $b_1,b_2,\ldots,b_n$ of length $n$. He defines the absolute beauty of the ar 阅读全文

摘要： G. Unusual Entertainment A tree is a connected graph without cycles. A permutation is an array consisting of $n$ distinct integers from $1$ to $n$ in 阅读全文

摘要： 最近接触到一些 DFS 序的题，它可以用来解决一些关于子树的问题。 DFS 序本质就是一棵树在深度优先搜索时访问节点的顺序。比如有下面一棵树，其 DFS 序就是 $1 \; 2 \; 4 \; 7 \; 8 \; 5 \; 3 \; 6 \; 9$。 DFS 序有一个很重要的性质，以节点 $u$ 为 阅读全文