| 82 | Remove Duplicates from Sorted List II | Linked ListTwo Pointers | Medium |
| 86 | Partition List | Linked ListTwo Pointers | Medium |
| 89 | Gray Code | MathBacktrackingBit Manipulation | Medium |
| 90 | Subsets II | ArrayBacktrackingBit Manipulation | Medium |
| 91 | Decode Ways | StringDynamic Programming | Medium |
| 92 | Reverse Linked List II | Linked List | Medium |
| 93 | Restore IP Addresses | StringBacktracking | Medium |
| 95 | Unique Binary Search Trees II | Dynamic ProgrammingBacktrackingTree+2 | Medium |
| 96 | Unique Binary Search Trees | MathDynamic ProgrammingTree+2 | Medium |
| 97 | Interleaving String | StringDynamic Programming | Medium |
| 98 | Validate Binary Search Tree | TreeDepth-First SearchBinary Search Tree+1 | Medium |
| 99 | Recover Binary Search Tree | TreeDepth-First SearchBinary Search Tree+1 | Medium |
| 102 | Binary Tree Level Order Traversal | TreeBreadth-First SearchBinary Tree | Medium |
| 103 | Binary Tree Zigzag Level Order Traversal | TreeBreadth-First SearchBinary Tree | Medium |
| 105 | Construct Binary Tree from Preorder and Inorder Traversal | ArrayHash TableDivide and Conquer+2 | Medium |
| 106 | Construct Binary Tree from Inorder and Postorder Traversal | ArrayHash TableDivide and Conquer+2 | Medium |
| 107 | Binary Tree Level Order Traversal II | TreeBreadth-First SearchBinary Tree | Medium |
| 109 | Convert Sorted List to Binary Search Tree | Linked ListDivide and ConquerTree+2 | Medium |
| 113 | Path Sum II | BacktrackingTreeDepth-First Search+1 | Medium |
| 114 | Flatten Binary Tree to Linked List | Linked ListStackTree+2 | Medium |
| 116 | Populating Next Right Pointers in Each Node | Linked ListTreeDepth-First Search+2 | Medium |
| 117 | Populating Next Right Pointers in Each Node II | Linked ListTreeDepth-First Search+2 | Medium |
| 120 | Triangle | ArrayDynamic Programming | Medium |
| 122 | Best Time to Buy and Sell Stock II | ArrayDynamic ProgrammingGreedy | Medium |
| 128 | Longest Consecutive Sequence | ArrayHash TableUnion Find | Medium |
| 129 | Sum Root to Leaf Numbers | TreeDepth-First SearchBinary Tree | Medium |
| 130 | Surrounded Regions | ArrayDepth-First SearchBreadth-First Search+2 | Medium |
| 131 | Palindrome Partitioning | StringDynamic ProgrammingBacktracking | Medium |
| 133 | Clone Graph | Hash TableDepth-First SearchBreadth-First Search+1 | Medium |
| 134 | Gas Station | ArrayGreedy | Medium |
| 137 | Single Number II | ArrayBit Manipulation | Medium |
| 138 | Copy List with Random Pointer | Hash TableLinked List | Medium |
| 139 | Word Break | ArrayHash TableString+3 | Medium |
| 142 | Linked List Cycle II | Hash TableLinked ListTwo Pointers | Medium |
| 143 | Reorder List | Linked ListTwo PointersStack+1 | Medium |
| 146 | LRU Cache | Hash TableLinked ListDesign+1 | Medium |
| 147 | Insertion Sort List | Linked ListSorting | Medium |
| 148 | Sort List | Linked ListTwo PointersDivide and Conquer+2 | Medium |
| 150 | Evaluate Reverse Polish Notation | ArrayMathStack | Medium |
| 151 | Reverse Words in a String | Two PointersString | Medium |
| 152 | Maximum Product Subarray | ArrayDynamic Programming | Medium |
| 153 | Find Minimum in Rotated Sorted Array | ArrayBinary Search | Medium |
| 155 | Min Stack | StackDesign | Medium |
| 162 | Find Peak Element | ArrayBinary Search | Medium |
| 164 | Maximum Gap | ArraySortingBucket Sort+1 | Medium |
| 165 | Compare Version Numbers | Two PointersString | Medium |
| 166 | Fraction to Recurring Decimal | Hash TableMathString | Medium |
| 167 | Two Sum II - Input Array Is Sorted | ArrayTwo PointersBinary Search | Medium |
| 172 | Factorial Trailing Zeroes | Math | Medium |
| 173 | Binary Search Tree Iterator | StackTreeDesign+3 | Medium |