Featured Lists Top 20 Problems on Dynamic programming Top 10 Problems on Backtracking Top 20 Problems on Graph Top 25 Problems on Trees Top 10 Problems on Bits Manipulation Top 15 Problems in LinkedList All Problems # Status Problem video Level Completes Likes 378 Longest contiguous character in a given String - O(N) Solution Beginner % 0 377 Convert Postfix to Infix Expression Medium % 0 376 Collatz Conjecture - Steps to transform Number to 1 Beginner % 0 375 String to Integer (AtoI - ASCII to Integer) Beginner % 1 374 Find all Prime Numbers less than equal to N | Set 1 Beginner % 0 373 Longest substring with at most two unique characters Medium % 0 372 Monotone Increasing Digits - Leetcode Medium % 1 371 Convert Infix to Prefix Expression Medium % 0 370 Find third largest element in a given array Beginner % 0 369 Find duplicates Characters in the given String Beginner % 0 368 Max Flow Problem - Ford-Fulkerson Algorithm Hard % 0 367 Sum of all Unique elements in a given array Beginner % 0 366 Java program to find the largest element in array Beginner % 0 365 Convert Infix to Postfix Expression Medium % 0 364 Find three smallest elements in a given array Beginner % 0 363 Evaluation of Infix expressions Medium % 0 362 Stack Java Class - Explained Beginner % 0 361 Convert Prefix to Infix Expression Medium % 0 360 Least Recently Used (LRU) Cache – Using LinkedHashSet and Deque | Set 2 Hard % 0 359 Merge K sorted Linked List - Using Priority Queue Hard % 0 358 Infix, Postfix and Prefix Notations/Expressions Beginner % 0 357 Count Set bits in a given Number Beginner % 1 356 Check if array contains all unique or distinct numbers Beginner % 0 355 Product of all Unique elements in a given array Beginner % 0 354 Valid Multiple Parentheses Medium % 1 353 Reverse a given number Beginner % 1 352 Check if given number is perfect square - O(√N) Solution Beginner % 0 351 Least Recently Used (LRU) Cache – Using HashMap and Doubly Linked List | Set 1 Hard % 1 350 Find first three largest elements in a given array Beginner % 0 349 Selection Sort Beginner % 0 348 Print Number with its Sign in Java Beginner % 0 347 Find the nearest building which has bike | Find nearest specific vertex from source in a graph. Hard % 0 346 Valid Brackets – Part 2 | Stack Method Beginner % 0 345 Find the roots of Quadratic Equation – Java Program Beginner % 0 344 Given two strings validate the output string Beginner % 0 Longest contiguous character in a given String - O(N) Solution Convert Postfix to Infix Expression Collatz Conjecture - Steps to transform Number to 1 String to Integer (AtoI - ASCII to Integer) Find all Prime Numbers less than equal to N | Set 1 Longest substring with at most two unique characters Monotone Increasing Digits - Leetcode Convert Infix to Prefix Expression Find third largest element in a given array Find duplicates Characters in the given String Max Flow Problem - Ford-Fulkerson Algorithm Sum of all Unique elements in a given array Java program to find the largest element in array Convert Infix to Postfix Expression Find three smallest elements in a given array Evaluation of Infix expressions Stack Java Class - Explained Convert Prefix to Infix Expression Least Recently Used (LRU) Cache – Using LinkedHashSet and Deque | Set 2 Merge K sorted Linked List - Using Priority Queue Infix, Postfix and Prefix Notations/Expressions Count Set bits in a given Number Check if array contains all unique or distinct numbers Product of all Unique elements in a given array Valid Multiple Parentheses Reverse a given number Check if given number is perfect square - O(√N) Solution Least Recently Used (LRU) Cache – Using HashMap and Doubly Linked List | Set 1 Find first three largest elements in a given array Selection Sort Print Number with its Sign in Java Find the nearest building which has bike | Find nearest specific vertex from source in a graph. Valid Brackets – Part 2 | Stack Method Find the roots of Quadratic Equation – Java Program Given two strings validate the output string 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16