DE Shaw

5 problems asked at DE Shaw.

Easy (2)

Two Sum (Leetcode 1)

Two Pointers, Arrays

Valid Parentheses (Leetcode 20)

Stack, Strings

Medium (1)

Remove Duplicate Letters / Smallest Subsequence of Distinct Characters (Leetcode 316 / 1081)

Strings, Greedy, Hashing...

Hard (2)

Maximal Rectangle (Leetcode 85) (largest rectangle with all 1's)

Matrix, Stack

Trapping Rain Water (LC 42)

Two Pointers, Prefix and Suffix Arrays, Stack