# DE Shaw Internship Experience

• Difficulty Level : Hard
• Last Updated : 30 Jul, 2018

Round 1: It was an online coding round. Two problems in 45 minutes –

• An easy problem. Simply based on sorting the given data based on some indices using pair in c+
• You are given a string. You can perform two operations –
• Erase the entire string.
• Erase a prefix s[0:i], only if s[0:i] = s[i:2*i].

Find the maximum number of operations to erase the entire string.

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Around 15 students were shortlisted.

Round 2: Technical Round

He asked me my favorite programming language. I said C++. He asked some really good problems on OOPS. Mostly based on virtual functions and runtime polymorphism. Then asked How will I make a class non-inheritable? Just go through all the articles here based on OOPS. Then he asked me an algorithmic problem based on binary search. Then he asked a few questions on operating systems involving Belady’s anomaly, page replacement algorithms. Then finally another algorithmic problem which to accommodate N people in M rooms with k constraints such that two people can’t be in the same room.

Round 3: HR/Puzzle Round

He asked to tell me something about myself that is not on my resume. I said that I love cricket and am a fan of msd. He asked why msd. Then he said prove me that you follow him. Then he started with puzzles about 8-9 puzzles –

1. A truck driver is going opposite traffic on a one-way street. 10 police officer saw him but doesn’t arrest him. Why didn’t the police officer stop him?
2. Number of rectangles in a chess board. I answered quickly. Number of polygons in a chessboard.
3. You are in a dark room where a table is kept. There are 50 coins placed on the table, out of which 10 coins are showing tails and 40 coins are showing heads. The task is to divide this set of 50 coins into 2 groups (not necessarily same size) such that both groups have same number of coins showing the tails.
4. A problem on probability. Easy.
5. Print numbers from 1 to 100 without using any loops or recursion.
6. Three switches three bulb puzzle.
7. 5 lanes 25 horses puzzle. Find best 3 in minimum number of races.
8. A simple dp problem.

Round 4: HR Round