Educational Codeforces Round 159 (Rated for Div. 2) E. Collapsing Strings

Educational Codeforces Round 159 (Rated for Div. 2) D. Robot Queries

Codeforces Round 909 (Div. 3) G. Unusual Entertainment

2053. Kth Distinct String in an Array

A distinct string is a string that is present only once in an array.

Given an array of strings arr, and an integer k, return the kth *distinct string present in arr. If there are fewer than k distinct strings, return an empty string* "".

Note that the strings are considered in the order in which they appear in the array.

3244. Shortest Distance After Road Addition Queries II

You are given an integer n and a 2D integer array queries.

There are n cities numbered from 0 to n - 1. Initially, there is a unidirectional road from city i to city i + 1 for all 0 <= i < n - 1.

queries[i] = [ui, vi] represents the addition of a new unidirectional road from city ui to city vi. After each query, you need to find the length of the shortest path from city 0 to city n - 1.

There are no two queries such that queries[i][0] < queries[j][0] < queries[i][1] < queries[j][1].

Return an array answer where for each i in the range [0, queries.length - 1], answer[i] is the length of the shortest path from city 0 to city n - 1 after processing the first i + 1 queries.

3243. Shortest Distance After Road Addition Queries I

You are given an integer n and a 2D integer array queries.

There are n cities numbered from 0 to n - 1. Initially, there is a unidirectional road from city i to city i + 1 for all 0 <= i < n - 1.

queries[i] = [ui, vi] represents the addition of a new unidirectional road from city ui to city vi. After each query, you need to find the length of the shortest path from city 0 to city n - 1.

Return an array answer where for each i in the range [0, queries.length - 1], answer[i] is the length of the shortest path from city 0 to city n - 1 after processing the first i + 1 queries.

3242. Design Neighbor Sum Service

You are given a n x n 2D array grid containing distinct elements in the range [0, n2 - 1].

Implement the neighborSum class:

• neighborSum(int [][]grid) initializes the object.
• int adjacentSum(int value) returns the sum of elements which are adjacent neighbors of value, that is either to the top, left, right, or bottom of value in grid.
• int diagonalSum(int value) returns the sum of elements which are diagonal neighbors of value, that is either to the top-left, top-right, bottom-left, or bottom-right of value in grid.

3245. Alternating Groups III

There are some red and blue tiles arranged circularly. You are given an array of integers colors and a 2D integers array queries.

The color of tile i is represented by colors[i]:

• colors[i] == 0 means that tile i is red.
• colors[i] == 1 means that tile i is blue.

An alternating group is a contiguous subset of tiles in the circle with alternating colors (each tile in the group except the first and last one has a different color from its adjacent tiles in the group).

You have to process queries of two types:

• queries[i] = [1, sizei], determine the count of alternating groups with size sizei.
• queries[i] = [2, indexi, colori], change colors[indexi] to colori.

Return an array answer containing the results of the queries of the first type in order.

Note that since colors represents a circle, the first and the last tiles are considered to be next to each other.

3241. Time Taken to Mark All Nodes

There exists an undirected tree with n nodes numbered 0 to n - 1. You are given a 2D integer array edges of length n - 1, where edges[i] = [ui, vi] indicates that there is an edge between nodes ui and vi in the tree.

Initially, all nodes are unmarked. For each node i:

• If i is odd, the node will get marked at time x if there is at least one node adjacent to it which was marked at time x - 1.
• If i is even, the node will get marked at time x if there is at least one node adjacent to it which was marked at time x - 2.

Return an array times where times[i] is the time when all nodes get marked in the tree, if you mark node i at time t = 0.

Note that the answer for each times[i] is independent, i.e. when you mark node i all other nodes are unmarked.

3240. Minimum Number of Flips to Make Binary Grid Palindromic II

You are given an m x n binary matrix grid.

A row or column is considered palindromic if its values read the same forward and backward.

You can flip any number of cells in grid from 0 to 1, or from 1 to 0.

Return the minimum number of cells that need to be flipped to make all rows and columns palindromic, and the total number of 1‘s in grid divisible by 4.