Visa

8 problems asked at Visa.

Easy (2)

Two Sum (Leetcode 1)

Two Pointers, Arrays

Valid Parentheses (Leetcode 20)

Stack, Strings

Medium (2)

Gas Station (Leetcode 134)

Arrays, Greedy, Prefix Sum

Group Anagrams (Leetcode 49)

Arrays, Strings, Sorting...

Hard (3)

Largest Rectangle in Histogram (leetcode 84)

Arrays, Stack

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

Matrix, 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