Curated List of Top 75 LeetCode

LeetCodeQuestions.md

Array

• Two Sum
• Best Time to Buy and Sell Stock
• Contains Duplicate
• Product of Array Except Self
• Maximum Subarray
• Maximum Product Subarray
• Find Minimum in Rotated Sorted Array
• Search in Rotated Sorted Array
• 3Sum
• Container With Most Water

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Binary

• Sum of Two Integers
• Number of 1 Bits
• Counting Bits
• Missing Number
• Reverse Bits

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Dynamic Programming

• Climbing Stairs
• Coin Change
• Longest Increasing Subsequence
• Longest Common Subsequence
• Word Break Problem
• Combination Sum
• House Robber
• House Robber II
• Decode Ways
• Unique Paths
• Jump Game

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Graph

• Clone Graph
• Course Schedule
• Pacific Atlantic Water Flow
• Number of Islands
• Longest Consecutive Sequence
• Alien Dictionary (Leetcode Premium)
• Graph Valid Tree (Leetcode Premium)
• Number of Connected Components in an Undirected Graph (Leetcode Premium)

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Interval

• Insert Interval
• Merge Intervals
• Non-overlapping Intervals
• Meeting Rooms (Leetcode Premium)
• Meeting Rooms II (Leetcode Premium)

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Linked List

• Reverse a Linked List
• Detect Cycle in a Linked List
• Merge Two Sorted Lists
• Merge K Sorted Lists
• Remove Nth Node From End Of List
• Reorder List

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Matrix

• Set Matrix Zeroes
• Spiral Matrix
• Rotate Image
• Word Search

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String

• Longest Substring Without Repeating Characters
• Longest Repeating Character Replacement
• Minimum Window Substring
• Valid Anagram
• Group Anagrams
• Valid Parentheses
• Valid Palindrome
• Longest Palindromic Substring
• Palindromic Substrings
• Encode and Decode Strings (Leetcode Premium)

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Tree

• Maximum Depth of Binary Tree
• Same Tree
• Invert/Flip Binary Tree
• Binary Tree Maximum Path Sum
• Binary Tree Level Order Traversal
• Serialize and Deserialize Binary Tree
• Subtree of Another Tree
• Construct Binary Tree from Preorder and Inorder Traversal
• Validate Binary Search Tree
• Kth Smallest Element in a BST
• Lowest Common Ancestor of BST
• Implement Trie (Prefix Tree)
• Add and Search Word
• Word Search II

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Heap

• Merge K Sorted Lists
• Top K Frequent Elements
• Find Median from Data Stream

string convertions and validations

• String to Integer (atoi)
• Integer to English Words
• Valid Number

Important Link:

14 Patterns to Ace Any Coding Interview Question

Merge K Sorted Lists

class Solution:
    def mergeKLists(self, lists: List[Optional[ListNode]]) -> Optional[ListNode]:
        heap = []
        for idx, headlistnode in enumerate(lists):
            if headlistnode:
                heap.append((headlistnode.val, idx))
        
        # sort asc accourding to list node val
        heapq.heapify(heap)
        # dummy node
        head = ListNode()
        cur = head
        while heap:
            min_val, idx = heapq.heappop(heap)
            new_node = ListNode(min_val)
            cur.next = new_node
            cur = cur.next
            
            # push next val from idx list onto heap
            push_node = lists[idx] = lists[idx].next
            if push_node:
                heapq.heappush(heap, (push_node.val, idx))
        return head.next

String to Integer (atoi)
https://leetcode.com/submissions/detail/574279356/