Contest Experiences | AtCoder Regular Contest #165

Atcoder is an Online Platform where coder come and solve the questions to gain experience of coding, during interviews and also make their foundation strong. There are different types of contests Available on their platform such as AHC (AtCoder Heuristic Contest), AGC (AtCoder Grand Contest), ARC (AtCoder Regular Contest), and ABC(AtCoder Beginner Contest). In this article, we will discuss about ARC Contest 165.

About the Contest | AtCoder Regular Contest #165:

• Contest Date: 17/Sept/2023.
• Contest Time: 05:30 pm (IST)
• Duration: 120 minutes
• Number of Questions: 6
• Question-wise point values: 400-600-600-700-700-800
• Contest Rule: you get a score assigned to it.
• Rank Computed: From the total marks of Question- [(the time you spend to get your current score) + (5 minutes) * (the number of incorrect attempts)].

Link of the Contest: https://atcoder.jp/contests/arc165

Overview of the questions asked:

Problem Name	Difficulty	Pre-Requisite	Approx. Time to Solve
Sum Equals LCM	Easy-Medium	LCM Triplet	10 min
Sliding Window Sort 2	Medium	lexicographical order	20 min
Social Distance on Graph	Medium	undirected Graph Color	20 min
Substring Comparison	Medium-Hard	lexicographical order	30 min
Random Isolation	Medium-Hard	expected value modulo mod	30 min
Make Adjacent	Hard	lexicographical order	unable to solve

Problem 1: Sum Equals LCM

This question is Straight Forward, for a given value of N we have to check the sum of their LCM is equal to N.

Problem 2: Sliding Window Sort

For solving this question you must have a good hands on Lexicographical concept. This problem is bit tricky. You have to find largest possible arrangement of number that will come last when sorted in dictionary order.

Problem 3: Social Distance on Graph

The Pre-requsite of the question is to know about the Simple Path in undirected Graph and once you done with the concept you have to find the minimum weight of a simple path connecting vertices of the same color.

Problem 4: Substring Comparison

In this question, you have asked to find list of 4 whole number(A,B,C,D) in which the sub-list of X from position A to B should be lexicographically smaller than the sub-list of X from position C to D.

Problem 5: Random Isolation

The question is asking to find the average number of time a certain action is performed In a Tree. Also, find the remainder by dividing the average by 998244353

Problem 6: Make Adjacent

You have to make ‘good sequence’ by minimum number of swaps in which the pair of adjacent value are same. Unfortunately, i was unable to solve this question.

Conclusion:

This contest is tough and also if you are beginner then don’t give ARC(Atcoder Regular Contest) start with easy question in ABC(Atcoder Beginer Contest). Also, if your goal is only to crack placement then this much won’t be required. But if your goal is to mastering Competative Programming then this platform is for you.