| 1 | Two Sum | ArrayHash Table | Easy |
| 9 | Palindrome Number | Math | Easy |
| 13 | Roman to Integer | Hash TableMathString | Easy |
| 14 | Longest Common Prefix | ArrayStringTrie | Easy |
| 20 | Valid Parentheses | StringStack | Easy |
| 21 | Merge Two Sorted Lists | Linked ListRecursion | Easy |
| 26 | Remove Duplicates from Sorted Array | ArrayTwo Pointers | Easy |
| 27 | Remove Element | ArrayTwo Pointers | Easy |
| 28 | Find the Index of the First Occurrence in a String | Two PointersStringString Matching | Easy |
| 35 | Search Insert Position | ArrayBinary Search | Easy |
| 58 | Length of Last Word | String | Easy |
| 66 | Plus One | ArrayMath | Easy |
| 67 | Add Binary | MathStringBit Manipulation+1 | Easy |
| 69 | Sqrt(x) | MathBinary Search | Easy |
| 70 | Climbing Stairs | MathDynamic ProgrammingMemoization | Easy |
| 83 | Remove Duplicates from Sorted List | Linked List | Easy |
| 88 | Merge Sorted Array | ArrayTwo PointersSorting | Easy |
| 94 | Binary Tree Inorder Traversal | StackTreeDepth-First Search+1 | Easy |
| 100 | Same Tree | TreeDepth-First SearchBreadth-First Search+1 | Easy |
| 101 | Symmetric Tree | TreeDepth-First SearchBreadth-First Search+1 | Easy |
| 104 | Maximum Depth of Binary Tree | TreeDepth-First SearchBreadth-First Search+1 | Easy |
| 108 | Convert Sorted Array to Binary Search Tree | ArrayDivide and ConquerTree+2 | Easy |
| 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 |
| 118 | Pascal's Triangle | ArrayDynamic Programming | Easy |
| 119 | Pascal's Triangle II | ArrayDynamic Programming | Easy |
| 121 | Best Time to Buy and Sell Stock | ArrayDynamic Programming | Easy |
| 125 | Valid Palindrome | Two PointersString | Easy |
| 136 | Single Number | ArrayBit Manipulation | Easy |
| 141 | Linked List Cycle | Hash TableLinked ListTwo Pointers | Easy |
| 144 | Binary Tree Preorder Traversal | StackTreeDepth-First Search+1 | Easy |
| 145 | Binary Tree Postorder Traversal | StackTreeDepth-First Search+1 | Easy |
| 160 | Intersection of Two Linked Lists | Hash TableLinked ListTwo Pointers | Easy |
| 168 | Excel Sheet Column Title | MathString | Easy |
| 169 | Majority Element | ArrayHash TableDivide and Conquer+2 | Easy |
| 171 | Excel Sheet Column Number | MathString | Easy |
| 175 | Combine Two Tables | Database | Easy |
| 181 | Employees Earning More Than Their Managers | Database | Easy |
| 182 | Duplicate Emails | Database | Easy |
| 183 | Customers Who Never Order | Database | Easy |
| 190 | Reverse Bits | Divide and ConquerBit Manipulation | Easy |
| 191 | Number of 1 Bits | Divide and ConquerBit Manipulation | Easy |
| 193 | Valid Phone Numbers | Shell | Easy |
| 195 | Tenth Line | Shell | Easy |
| 196 | Delete Duplicate Emails | Database | Easy |
| 197 | Rising Temperature | Database | Easy |
| 202 | Happy Number | Hash TableMathTwo Pointers | Easy |
| 203 | Remove Linked List Elements | Linked ListRecursion | Easy |
| 205 | Isomorphic Strings | Hash TableString | Easy |