| 1 | Two Sum | Easy | 1116 | arrayhash-table |
| 9 | Palindrome Number | Easy | 1168 | math |
| 13 | Roman to Integer | Easy | 1258 | hash-tablemathstring |
| 14 | Longest Common Prefix | Easy | 1170 | stringtrie |
| 20 | Valid Parentheses | Easy | 1211 | stringstack |
| 21 | Merge Two Sorted Lists | Easy | 1168 | linked-listrecursion |
| 26 | Remove Duplicates from Sorted Array | Easy | 1169 | arraytwo-pointers |
| 27 | Remove Element | Easy | 1153 | arraytwo-pointers |
| 28 | Find the Index of the First Occurrence in a String | Easy | 1302 | two-pointersstringstring-matching |
| 35 | Search Insert Position | Easy | 1164 | arraybinary-search |
| 58 | Length of Last Word | Easy | 1156 | string |
| 66 | Plus One | Easy | 1151 | arraymath |
| 67 | Add Binary | Easy | 1160 | mathstringbit-manipulation+1 |
| 69 | Sqrt(x) | Easy | 1178 | mathbinary-search |
| 70 | Climbing Stairs | Easy | 1232 | mathdynamic-programmingmemoization |
| 83 | Remove Duplicates from Sorted List | Easy | 1169 | linked-list |
| 88 | Merge Sorted Array | Easy | 1165 | arraytwo-pointerssorting |
| 94 | Binary Tree Inorder Traversal | Easy | 1250 | stacktreedepth-first-search+1 |
| 100 | Same Tree | Easy | 1176 | treedepth-first-searchbreadth-first-search+1 |
| 101 | Symmetric Tree | Easy | 1200 | treedepth-first-searchbreadth-first-search+1 |
| 104 | Maximum Depth of Binary Tree | Easy | 1116 | treedepth-first-searchbreadth-first-search+1 |
| 108 | Convert Sorted Array to Binary Search Tree | Easy | 1281 | arraydivide-and-conquertree+2 |
| 110 | Balanced Binary Tree | Easy | 1194 | treedepth-first-searchbinary-tree |
| 111 | Minimum Depth of Binary Tree | Easy | 1248 | treedepth-first-searchbreadth-first-search+1 |
| 112 | Path Sum | Easy | 1181 | treedepth-first-searchbreadth-first-search+1 |
| 118 | Pascal's Triangle | Easy | 1168 | arraydynamic-programming |
| 119 | Pascal's Triangle II | Easy | 1178 | arraydynamic-programming |
| 121 | Best Time to Buy and Sell Stock | Easy | 1487 | arraydynamic-programming |
| 125 | Valid Palindrome | Easy | 1138 | two-pointersstring |
| 136 | Single Number | Easy | 1150 | arraybit-manipulation |
| 141 | Linked List Cycle | Easy | 1302 | hash-tablelinked-listtwo-pointers |
| 144 | Binary Tree Preorder Traversal | Easy | 1258 | stacktreedepth-first-search+1 |
| 145 | Binary Tree Postorder Traversal | Easy | 1214 | stacktreedepth-first-search+1 |
| 160 | Intersection of Two Linked Lists | Easy | 1495 | linked-listhash-tabletwo-pointers |
| 163 | Missing Ranges | Easy | 1246 | array |
| 168 | Excel Sheet Column Title | Easy | — | mathstring |
| 169 | Majority Element | Easy | 1235 | arrayhash-tabledivide-and-conquer+2 |
| 190 | Reverse Bits | Easy | 1149 | divide-and-conquerbit-manipulation |
| 191 | Number of 1 Bits | Easy | 1088 | divide-and-conquerbit-manipulation |
| 202 | Happy Number | Easy | 1188 | hash-tablemathtwo-pointers |
| 203 | Remove Linked List Elements | Easy | 1222 | linked-listrecursion |
| 205 | Isomorphic Strings | Easy | 1262 | hash-tablestring |
| 206 | Reverse Linked List | Easy | 1186 | linked-listrecursion |
| 217 | Contains Duplicate | Easy | 1160 | arrayhash-tablesorting |
| 219 | Contains Duplicate II | Easy | 1320 | arrayhash-tablesliding-window |
| 222 | Count Complete Tree Nodes | Easy | 1375 | binary-searchtreedepth-first-search+1 |
| 225 | Implement Stack using Queues | Easy | — | stackdesignqueue |
| 226 | Invert Binary Tree | Easy | 1160 | treedepth-first-searchbreadth-first-search+1 |
| 228 | Summary Ranges | Easy | 1192 | array |
| 231 | Power of Two | Easy | 1154 | mathbit-manipulationrecursion |