| 101 | Symmetric Tree | TreeDepth-First SearchBreadth-First Search+1 | Easy |
| 102 | Binary Tree Level Order Traversal | TreeBreadth-First SearchBinary Tree | Medium |
| 103 | Binary Tree Zigzag Level Order Traversal | TreeBreadth-First SearchBinary Tree | Medium |
| 104 | Maximum Depth of Binary Tree | TreeDepth-First SearchBreadth-First Search+1 | Easy |
| 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 |
| 108 | Convert Sorted Array to Binary Search Tree | ArrayDivide and ConquerTree+2 | Easy |
| 109 | Convert Sorted List to Binary Search Tree | Linked ListDivide and ConquerTree+2 | Medium |
| 110 | Balanced Binary Tree | TreeDepth-First SearchBinary Tree | Easy |
| 111 | Minimum Depth of Binary Tree | TreeDepth-First SearchBreadth-First Search+1 | Easy |
| 112 | Path Sum | TreeDepth-First SearchBreadth-First Search+1 | Easy |
| 113 | Path Sum II | BacktrackingTreeDepth-First Search+1 | Medium |
| 114 | Flatten Binary Tree to Linked List | Linked ListStackTree+2 | Medium |
| 115 | Distinct Subsequences | StringDynamic Programming | Hard |
| 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 |
| 118 | Pascal's Triangle | ArrayDynamic Programming | Easy |
| 119 | Pascal's Triangle II | ArrayDynamic Programming | Easy |
| 120 | Triangle | ArrayDynamic Programming | Medium |
| 121 | Best Time to Buy and Sell Stock | ArrayDynamic Programming | Easy |
| 122 | Best Time to Buy and Sell Stock II | ArrayDynamic ProgrammingGreedy | Medium |
| 123 | Best Time to Buy and Sell Stock III | ArrayDynamic Programming | Hard |
| 124 | Binary Tree Maximum Path Sum | Dynamic ProgrammingTreeDepth-First Search+1 | Hard |
| 125 | Valid Palindrome | Two PointersString | Easy |
| 126 | Word Ladder II | Hash TableStringBacktracking+1 | Hard |
| 127 | Word Ladder | Hash TableStringBreadth-First Search | Hard |
| 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 |
| 132 | Palindrome Partitioning II | StringDynamic Programming | Hard |
| 133 | Clone Graph | Hash TableDepth-First SearchBreadth-First Search+1 | Medium |
| 134 | Gas Station | ArrayGreedy | Medium |
| 135 | Candy | ArrayGreedy | Hard |
| 136 | Single Number | ArrayBit Manipulation | Easy |
| 137 | Single Number II | ArrayBit Manipulation | Medium |
| 138 | Copy List with Random Pointer | Hash TableLinked List | Medium |
| 139 | Word Break | ArrayHash TableString+3 | Medium |
| 140 | Word Break II | ArrayHash TableString+4 | Hard |
| 141 | Linked List Cycle | Hash TableLinked ListTwo Pointers | Easy |
| 142 | Linked List Cycle II | Hash TableLinked ListTwo Pointers | Medium |
| 143 | Reorder List | Linked ListTwo PointersStack+1 | Medium |
| 144 | Binary Tree Preorder Traversal | StackTreeDepth-First Search+1 | Easy |
| 145 | Binary Tree Postorder Traversal | StackTreeDepth-First Search+1 | Easy |
| 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 |
| 149 | Max Points on a Line | ArrayHash TableMath+1 | Hard |
| 150 | Evaluate Reverse Polish Notation | ArrayMathStack | Medium |