open_problems.txt

Problem ID marked with leading ~ indicates there's good evidences that the algorithm we provide is hard to improve. Leading + indicates the original problem is solved, but there exists some interesting follow-up questions.

+116 Populating Next Right Pointers in Each Node  
+225 Implement Stack using Queues  
+234 Palindrome Linked List  
264 Ugly Number II  
~302 Smallest Rectangle Enclosing Black Pixels  
306 Additive Number  
317 Shortest Distance from All Buildings  
368 Largest Divisible Subset  
395 Longest Substring with At Least K Repeating Characters  
~403 Frog Jump  
411 Minimum Unique Word Abbreviation  
~464 Can I Win  
~483 Smallest Good Base  
522 Longest Uncommon Subsequence II  
548 Split Array with Equal Sum  
727 Minimum Window Subsequence  
~741 Cherry Pickup  
~762 Prime Number of Set Bits in Binary Representation  
787 Cheapest Flights Within K Stops  
818 Race Car  
837 New 21 Game  
839 Similar String Groups  
~898 Bitwise ORs of Subarrays  
1057 Campus Bikes  
~1074 Number of Submatrices That Sum to Target  
~1293 Shortest Path in a Grid with Obstacles Elimination  
1316 Distinct Echo Substrings  
~1334 Find the City With the Smallest Number of Neighbors at a Threshold Distance  
~1335 Minimum Difficulty of a Job Schedule  
1439 Find the Kth Smallest Sum of a Matrix With Sorted Rows  
1452 People Whose List of Favorite Companies Is Not a Subset of Another List  
1510 Stone Game IV  
1538 Guess the Majority in a Hidden Array  
1542 Find Longest Awesome Substring  
1548 The Most Similar Path in a Graph  
~1622 Fancy Sequence  
1627 Graph Connectivity With Threshold  
1630 Arithmetic Subarrays  
1638 Count Substrings That Differ by One Character  
1659 Maximize Grid Happiness  
~1681 Minimum Incompatibility  
~1707 Maximum XOR With an Element From Array  
1766 Tree of Coprimes  
1799 Maximize Score After N Operations  
~1819 Number of Different Subsequences GCDs  
~1849 Splitting a String Into Descending Consecutive Values  
1857 Largest Color Value in a Directed Graph  
~1878 Get Biggest Three Rhombus Sums in a Grid  
1898 Maximum Number of Removable Characters  
2002 Maximum Product of the Length of Two Palindromic Subsequences  
2013 Detect Squares  
2076 Process Restricted Friend Requests  
~2093 Minimum Cost to Reach City With Discounts  
2101 Detonate the Maximum Bombs  
2122 Recover the Original Array  
2322 Minimum Score After Removals on a Tree  
~2338 Count the Number of Ideal Arrays  
2440 Create Components With Same Value  
2462 Total Cost to Hire K Workers  




DP/counting:  
087 Scramble String  
312 Burst Balloons  
375 Guess Number Higher or Lower II  
514 Freedom Trail  
546 Remove Boxes  
576 Out of Boundary Paths  
629 K Inverse Pairs Array  
664 Strange Printer  
688 Knight Probability in Chessboard  
730 Count Different Palindromic Subsequences  
813 Largest Sum of Averages  
903 Valid Permutations for DI Sequence  
1039 Minimum Score Triangulation of Polygon  
1043 Partition Array for Maximum Sum  
1269 Number of Ways to Stay in the Same Place After Some Steps  
1278 Palindrome Partitioning III  
1397 Find All Good Strings  
1420 Build Array Where You Can Find The Maximum Exactly K Comparisons  
1444 Number of Ways of Cutting a Pizza  
1467 Probability of a Two Boxes Having The Same Number of Distinct Balls  
1563 Stone Game V  
1575 Count All Possible Routes  
1690 Stone Game VII  
1751 Maximum Number of Events That Can Be Attended II  
1770 Maximum Score from Performing Multiplication Operations  
1787 Make the XOR of All Segments Equal to Zero  
1883 Minimum Skips to Arrive at Meeting On Time  
1895 Largest Magic Square  
1925 Count Square Sum Triples  
1959 Minimum Total Space Wasted With K Resizing Operations  
1999 Smallest Greater Multiple Made of Two Digits  
2267 Check if There Is a Valid Parentheses String Path  
2466 Count Ways To Build Good Strings  
2478 Number of Beautiful Partitions  
2916 Subarrays Distinct Element Sum of Squares II  
3130 Find All Possible Stable Binary Arrays II  
3234 Count the Number of Substrings With Dominant Ones