Tag

#hash-map

37 posts

Valid Anagram (LeetCode 242)

The problem You get two strings and . Return if is an anagram of , meaning it…

Two Sum (LeetCode 1)

The problem You get an array of integers and an integer . Return the indices of…

Top K Frequent Elements (LeetCode 347)

The problem You get an integer array and an integer . Return the values that…

Time Based Key-Value Store (LeetCode 981)

The problem Design a class with two methods: stores for at time . returns…

Subarray Sums Divisible by K (LeetCode 974)

The problem Given an integer array (values may be negative) and an integer…

Subarray Sum Equals K (LeetCode 560)

The problem You get an integer array (values may be negative) and an integer…

Sort Characters By Frequency (LeetCode 451)

The problem You get a string . Rearrange it so that characters appear in order…

Roman to Integer (LeetCode 13)

The problem You get a valid Roman numeral as a string made of (1, 5, 10, 5…

Ransom Note (LeetCode 383)

The problem You get two strings, and . Each letter in the magazine can be used…

Permutation in String (LeetCode 567)

The problem You get two strings and . Return if some contiguous piece of is a…

Partition Labels (LeetCode 763)

The problem Given a string of lowercase letters, split it into as many parts as…

Next Greater Element I (LeetCode 496)

The problem You get two arrays of distinct integers, and , where every value in…

Minimum Window Substring (LeetCode 76)

The problem You get two strings and . Return the shortest substring of that…

Maximum Size Subarray Sum Equals k (LeetCode 325)

The problem Given an integer array (values can be negative) and an integer…

Majority Element (LeetCode 169)

The problem You get an array of length . One value, the majority element…

Map Sum Pairs (LeetCode 677)

The problem Design a class: stores . If the key already exists, the new value…

LRU Cache (LeetCode 146)

The problem Design a class that stores up to key-value pairs and supports…

Longest Substring Without Repeating Characters (LeetCode 3)

The problem You get a string . Return the length of the longest substring…

Longest Repeating Character Replacement (LeetCode 424)

The problem You get an uppercase string and an integer . You may change up to…

LFU Cache (LeetCode 460)

The problem Design a cache with a fixed that supports, in O(1) average time…

Insert Delete GetRandom O(1) (LeetCode 380)

The problem Design a with three operations, each in O(1) average time: : add…

Hand of Straights (LeetCode 846)

The problem You hold a hand of cards, each with an integer value, and a number…

Group Anagrams (LeetCode 49)

The problem You get a list of strings . Group together the words that are…

Isomorphic Strings (LeetCode 205)

The problem You get two strings and of the same length. They are isomorphic if…

Fruit Into Baskets (LeetCode 904)

The problem A row of trees is given as an array , where is the type of fruit on…

First Unique Character in a String (LeetCode 387)

The problem You get a string of lowercase letters. Return the index of the…

Find All Anagrams in a String (LeetCode 438)

The problem You get a string and a pattern . Return the list of every start…

Design Twitter (LeetCode 355)

The problem Design a simplified Twitter with four operations: : the user posts a…

Design HashMap (LeetCode 706)

The problem Implement a hash map for integer keys and values without using any…

Design Underground System (LeetCode 1396)

The problem Design a system that tracks passengers on a metro network…

Copy List with Random Pointer (LeetCode 138)

The problem Each node in a linked list has a , a pointer, and a pointer that…

Continuous Subarray Sum (LeetCode 523)

The problem Given an array of non-negative integers and an integer , return if…

Contiguous Array (LeetCode 525)

The problem Given a binary array (only 0s and 1s), return the length of the…

Construct Binary Tree from Preorder and Inorder (LeetCode 105)

The problem You get two lists for the same binary tree: its preorder traversal…

Accounts Merge (LeetCode 721)

The problem You get a list of accounts. Each account is a name followed by one…

Hash Maps & Frequency — Practice Problems

Thirteen problems that drill the hash map & frequency pattern from Lesson 6. The…

Hash Maps & Frequency Counting

The hash map is the most useful data structure in interviews. The core move is…

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