69eloChess's blog

By 69eloChess, history, 4 months ago, In English

Problem A :

1,2,3,4,.......n is an intutive and easy answer.

Difficulty: 5/10 for a A

Problem B

Search the whole matrix a on 2x2 small grids and keep changing the values accordingly till i=0,n-1. j=0,m-1. In the end you will check if the two matrices are now equal or not.

Difficulty: 9/10 for a B

Problem C

There are nine cases totally ABC, ACB, BAC, BCA, CAB, CBA now check for each case seprately and apply binary search to find the lower bound for total_sum/3. Implementation is kinda tough.

Difficulty: 8/10 for a C

Problem D

Just count number of inversions using merge sort/segment tree. If (count1-count2)%2==0 YES else NO. Corner case: check if a & b are a permutation of each other or not.

Difficulty: 5/10 for a D

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4 months ago, # |
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Why didn't you give the contest yourself?

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4 months ago, # |
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stop capping

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4 months ago, # |
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My thoughts on first div2 where i solved 4 probs:

A: very easy, just noticed that if you add a number to its multiple its always still gonna be a multiple of the original number

B: medium, I didn't get it at first glance and moved on, but when i came back and used some paper i got a general idea and implemented

C: medium difficulty but bad for me: no binary search needed, literally just brute force, for all the diff possible orders, just add until the temp sum is greater than the goal

D: easy for a D, just observation, no tree needed, just a simple map

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4 months ago, # |
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thanks for editorial