截止至今LeetCode题目总量已经有1582题，估计将来每年平均增长300题左右，大部分人肯定是刷不完的，所以得有选择地刷LeetCode。
一种公认的刷题策略是按类别刷题，可是每个类别也有许多题，在有限的时间里到底该刷哪些题呢？个人根据LeetCode官方给出的每个题目的出现频率，整理并收录了每个类别里高频出现的题目，对于官方统计频率太低的题目，不予收录，最终得到了这个高频题目表格。
例如，对于下图中题号#275与#270的题目将被收录，并且#275出现频率大于#270；而对于题号#1011与#1182的题目，因为出现频率太低，将不被收录：
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树结构篇-82题(Tree, 82 problems)
数据日期： 2020/03/26 (此时LeetCode题目数量：1582)
数据来源： LeetCode官方，将不同类别的题目按照官方给的出现频率(Frequency)降序排列，取有频率统计的题。
| 排序 | 题号 | 题目 | 通过率 | 难度 |
|---|---|---|---|---|
| 1 | #95 | Unique Binary Search Trees II | 0.623 | 中等 |
| 2 | #94 | Binary Tree Inorder Traversal | 0.707 | 中等 |
| 3 | #96 | Unique Binary Search Trees | 0.652 | 中等 |
| 4 | #226 | Invert Binary Tree | 0.745 | 简单 |
| 5 | #104 | Maximum Depth of Binary Tree | 0.726 | 简单 |
| 6 | #108 | Convert Sorted Array to Binary Search Tree | 0.699 | 简单 |
| 7 | #617 | Merge Two Binary Trees | 0.755 | 简单 |
| 8 | #107 | Binary Tree Level Order Traversal II | 0.647 | 简单 |
| 9 | #543 | Diameter of Binary Tree | 0.49 | 简单 |
| 10 | #114 | Flatten Binary Tree to Linked List | 0.681 | 中等 |
| 11 | #105 | Construct Binary Tree from Preorder and Inorder Traversal | 0.646 | 中等 |
| 12 | #101 | Symmetric Tree | 0.506 | 简单 |
| 13 | #687 | Longest Univalue Path | 0.394 | 简单 |
| 14 | #654 | Maximum Binary Tree | 0.798 | 中等 |
| 15 | #655 | Print Binary Tree | 0.553 | 中等 |
| 16 | #449 | Serialize and Deserialize BST | 0.51 | 中等 |
| 17 | #199 | Binary Tree Right Side View | 0.639 | 中等 |
| 18 | #257 | Binary Tree Paths | 0.63 | 简单 |
| 19 | #102 | Binary Tree Level Order Traversal | 0.613 | 中等 |
| 20 | #144 | Binary Tree Preorder Traversal | 0.648 | 中等 |
| 21 | #669 | Trim a Binary Search Tree | 0.646 | 简单 |
| 22 | #538 | Convert BST to Greater Tree | 0.596 | 简单 |
| 23 | #124 | Binary Tree Maximum Path Sum | 0.397 | 困难 |
| 24 | #112 | Path Sum | 0.493 | 简单 |
| 25 | #145 | Binary Tree Postorder Traversal | 0.707 | 困难 |
| 26 | #501 | Find Mode in Binary Search Tree | 0.441 | 简单 |
| 27 | #100 | Same Tree | 0.569 | 简单 |
| 28 | #530 | Minimum Absolute Difference in BST | 0.56 | 简单 |
| 29 | #222 | Count Complete Tree Nodes | 0.678 | 中等 |
| 30 | #111 | Minimum Depth of Binary Tree | 0.418 | 简单 |
| 31 | #637 | Average of Levels in Binary Tree | 0.637 | 简单 |
| 32 | #437 | Path Sum III | 0.545 | 简单 |
| 33 | #173 | Binary Search Tree Iterator | 0.718 | 中等 |
| 34 | #337 | House Robber III | 0.564 | 中等 |
| 35 | #653 | Two Sum IV - Input is a BST | 0.544 | 简单 |
| 36 | #404 | Sum of Left Leaves | 0.542 | 简单 |
| 37 | #110 | Balanced Binary Tree | 0.509 | 简单 |
| 38 | #776 | Split BST | 0.552 | 中等 |
| 39 | #99 | Recover Binary Search Tree | 0.559 | 困难 |
| 40 | #863 | All Nodes Distance K in Binary Tree | 0.477 | 中等 |
| 41 | #103 | Binary Tree Zigzag Level Order Traversal | 0.54 | 中等 |
| 42 | #563 | Binary Tree Tilt | 0.537 | 简单 |
| 43 | #684 | Redundant Connection | 0.571 | 中等 |
| 44 | #235 | Lowest Common Ancestor of a Binary Search Tree | 0.629 | 简单 |
| 45 | #515 | Find Largest Value in Each Tree Row | 0.585 | 中等 |
| 46 | #297 | Serialize and Deserialize Binary Tree | 0.458 | 困难 |
| 47 | #236 | Lowest Common Ancestor of a Binary Tree | 0.608 | 中等 |
| 48 | #513 | Find Bottom Left Tree Value | 0.688 | 中等 |
| 49 | #606 | Construct String from Binary Tree | 0.527 | 简单 |
| 50 | #652 | Find Duplicate Subtrees | 0.527 | 中等 |
| 51 | #113 | Path Sum II | 0.589 | 中等 |
| 52 | #106 | Construct Binary Tree from Inorder and Postorder Traversal | 0.675 | 中等 |
| 53 | #508 | Most Frequent Subtree Sum | 0.627 | 中等 |
| 54 | #230 | Kth Smallest Element in a BST | 0.694 | 中等 |
| 55 | #129 | Sum Root to Leaf Numbers | 0.624 | 中等 |
| 56 | #662 | Maximum Width of Binary Tree | 0.358 | 中等 |
| 57 | #783 | Minimum Distance Between BST Nodes | 0.52 | 简单 |
| 58 | #98 | Validate Binary Search Tree | 0.295 | 中等 |
| 59 | #572 | Subtree of Another Tree | 0.439 | 简单 |
| 60 | #671 | Second Minimum Node In a Binary Tree | 0.459 | 简单 |
| 61 | #450 | Delete Node in a BST | 0.392 | 中等 |
| 62 | #250 | Count Univalue Subtrees | 0.619 | 中等 |
| 63 | #685 | Redundant Connection II | 0.335 | 困难 |
| 64 | #623 | Add One Row to Tree | 0.505 | 中等 |
| 65 | #116 | Populating Next Right Pointers in Each Node | 0.564 | 中等 |
| 66 | #998 | Maximum Binary Tree II | 0.593 | 中等 |
| 67 | #255 | Verify Preorder Sequence in Binary Search Tree | 0.458 | 中等 |
| 68 | #333 | Largest BST Subtree | 0.421 | 中等 |
| 69 | #1008 | Construct Binary Search Tree from Preorder Traversal | 0.717 | 中等 |
| 70 | #117 | Populating Next Right Pointers in Each Node II | 0.464 | 中等 |
| 71 | #988 | Smallest String Starting From Leaf | 0.442 | 中等 |
| 72 | #270 | Closest Binary Search Tree Value | 0.506 | 简单 |
| 73 | #549 | Binary Tree Longest Consecutive Sequence II | 0.473 | 中等 |
| 74 | #582 | Kill Process | 0.346 | 中等 |
| 75 | #156 | Binary Tree Upside Down | 0.73 | 中等 |
| 76 | #285 | Inorder Successor in BST | 0.607 | 中等 |
| 77 | #272 | Closest Binary Search Tree Value II | 0.587 | 困难 |
| 78 | #666 | Path Sum IV | 0.585 | 中等 |
| 79 | #366 | Find Leaves of Binary Tree | 0.73 | 中等 |
| 80 | #536 | Construct Binary Tree from String | 0.513 | 中等 |
| 81 | #545 | Boundary of Binary Tree | 0.349 | 中等 |
| 82 | #298 | Binary Tree Longest Consecutive Sequence | 0.54 | 中等 |
相关/参考链接
leetcode-cn
leetcode