4 | Median of Two Sorted Arrays | Hard |
10 | Regular Expression Matching | Hard |
23 | Merge k Sorted Lists | Hard |
25 | Reverse Nodes in k-Group | Hard |
30 | Substring with Concatenation of All Words | Hard |
32 | Longest Valid Parentheses | Hard |
37 | Sudoku Solver | Hard |
41 | First Missing Positive | Hard |
42 | Trapping Rain Water | Hard |
44 | Wildcard Matching | Hard |
45 | Jump Game II | Hard |
51 | N-Queens | Hard |
52 | N-Queens II | Hard |
57 | Insert Interval | Hard |
65 | Valid Number | Hard |
68 | Text Justification | Hard |
72 | Edit Distance | Hard |
76 | Minimum Window Substring | Hard |
84 | Largest Rectangle in Histogram | Hard |
85 | Maximal Rectangle | Hard |
87 | Scramble String | Hard |
97 | Interleaving String | Hard |
99 | Recover Binary Search Tree | Hard |
115 | Distinct Subsequences | Hard |
123 | Best Time to Buy and Sell Stock III | Hard |
124 | Binary Tree Maximum Path Sum | Hard |
126 | Word Ladder II | Hard |
128 | Longest Consecutive Sequence | Hard |
132 | Palindrome Partitioning II | Hard |
135 | Candy | Hard |