DATE PROBLEM TOPIC SOLUTION IMPORTANT FEB 1 Best Time to Buy and Sell Stock DP 💡 FEB 2 Find All Anagrams in a String Sliding Window Solution 💡 FEB 3 4Sum II Hash Table Solution FEB 4 Contiguous Array Array Solution FEB 5 Merge k Sorted Lists Linked List 💡 FEB 6 Remove Duplicates from Sorted Array Array Solution FEB 7 Find The Difference String Solution FEB 8 Add Digits Number Theory FEB 9 K Different Pairs in an Array Array Solution 💡 FEB 10 SubArray Sum Equals K Array Solution 💡 FEB 11 Permutation in String String Solution 💡 FEB 12 Word Ladder String Solution FEB 13 Subsets Array Solution FEB 14 Maximum Depth of a Binary Tree Tree Solution 💡 FEB 15 Single Number Array Solution FEB 16 Swap Nodes in Pairs Linked List 💡 FEB 17 Combination Sum Array Solution 💡 FEB 18 Remove K Digits Stack Solution 💡 FEB 19 Minimize Deviation in Array Greedy Solution 💡 FEB 20 Remove Covered Intervals Sorting Solution 💡 FEB 21 Majority Element Array Solution FEB 22 Excel Sheet Column Number String FEB 23 Clone Graph Graph Solution 💡 FEB 24 Sort List Linked List Solution 💡 FEB 25 Compare Version Numbers String FEB 26 Shortest Path visiting all Nodes Tree 💡 FEB 27 Maximum Width of Binary Tree Tree 💡 FEB 28 Summary Ranges Array