Oracle

13 problems asked at Oracle.

Easy (3)

Top K Frequent Elements (Leetcode 347)

Arrays, Hashing, Heap...

Two Sum (Leetcode 1)

Two Pointers, Arrays

Valid Parentheses (Leetcode 20)

Stack, Strings

Medium (4)

Gas Station (Leetcode 134)

Arrays, Greedy, Prefix Sum

Group Anagrams (Leetcode 49)

Arrays, Strings, Sorting...

Longest Substring Without Repeating Characters (leetcode 3)

Sliding Window, Strings, Hashing

Min Stack (Leetcode 155)

Stack

Hard (5)

Largest Rectangle in Histogram (leetcode 84)

Arrays, Stack

N-Queens (Leetcode 51 & 52)

Backtracking, Maths, Recursion...

Next Permutation (Leetcode 31)

Arrays, Greedy, Two Pointers

Postfix to Infix & Evaluation of Postfix (Leetcode 150)

Stack

Trapping Rain Water (LC 42)

Two Pointers, Prefix and Suffix Arrays, Stack

Not Specified (1)

Best Time to Buy and Sell Stock

Arrays, DP