| 学习笔记 | |
| |#|Title|Solutions| | |
| |---|---|------| | |
| |242|[valid-anagram](https://leetcode-cn.com/problems/anagram) | 数组计数([Go](242/valid_anagram.go),[Py](242/valid_anagram.py))| | |
| |49|[group-anagrams](https://leetcode-cn.com/problems/group-anagrams) | 计数分类([Go](49/group_anagrams.go),[Py](49/group_anagrams.py))| | |
| |94|[binary-tree-inorder-traversal](https://leetcode-cn.com/problems/binary-tree-inorder-traversal) | 递归([Go](94/binary_tree_inorder_traversal.go),[Py](94/binary_tree_inorder_traversal.py)),栈([Go](94/binary_tree_inorder_traversal2.go),[Py](94/binary_tree_inorder_traversal2.py)), Morris遍历([Go](94/binary_tree_inorder_traversal3.go),[Py](94/binary_tree_inorder_traversal3.py))| | |
| |144|[binary-tree-preorder-traversal](https://leetcode-cn.com/problems/binary-tree-preorder-traversal) | 递归([Go](144/binary_tree_preorder_traversal.go),[Py](144/binary_tree_preorder_traversal.py)),栈([Go](144/binary_tree_preorder_traversal2.go),[Py](144/binary_tree_preorder_traversal2.py)), Morris遍历([Go](144/binary_tree_preorder_traversal3.go),[Py](144/binary_tree_preorder_traversal3.py))| | |
| |590|[n-ary-tree-postorder-traversal](https://leetcode-cn.com/problems/n-ary-tree-postorder-traversal) | 递归([Go](590/n_ary_tree_postorder_traversal.go),[Py](590/n_ary_tree_postorder_traversal.go)),栈([Go](590/n_ary_tree_postorder_traversal2.go),[Py](590/n_ary_tree_postorder_traversal2.go))| | |
| |589|[n-ary-tree-preorder-traversal](https://leetcode-cn.com/problems/n-ary-tree-preorder-traversal) | 递归([Go](589/n_ary_tree_preorder_traversal.go),[Py](589/n_ary_tree_preorder_traversal.go)),栈([Go](589/n_ary_tree_preorder_traversal2.go),[Py](589/n_ary_tree_preorder_traversal2.go))| | |
| |429|[n-ary-tree-level-order-traversal](https://leetcode-cn.com/problems/n-ary-tree-level-order-traversal) | 递归([Go](429/n_ary_tree_level_order_traversal.go),[Py](429/n_ary_tree_level_order_traversal.py)),栈([Go](429/n_ary_tree_level_order_traversal2.go),[Py](429/n_ary_tree_level_order_traversal2.py))| | |
| |LCOF40|[top-k](https://leetcode-cn.com/problems/zui-xiao-de-kge-shu-lcof/) | 大顶堆([Go](LCOF40/least_numbers.go),[Py](LCOF40/least_numbers.py)),快速搜索([Go](LCOF40/least_numbers2.go),[Py](LCOF40/least_numbers2.py))| | |
| |264|[ugly-number-ii](https://leetcode-cn.com/problems/ugly-number-ii) | 小顶堆([Go](264/ugly_number_ii.go),[Py](264/ugly_number_ii.py)), 三指针([Go](264/ugly_number_ii2.go),[Py](264/ugly_number_ii2.py))| | |
| |347|[top-k-frequent-elements](https://leetcode-cn.com/problems/top-k-frequent-elements) | 小顶堆([Go](347/top_k_frequent_elements.go),[Py](347/top_k_frequent_elements.go)), 快速搜索([Go](347/top_k_frequent_elements2.go))| | |
| ## 题解 | |
| ### 242. valid-anagram | |
| 使用长度为26的数组计数，s++, t-- | |
| ### 49. group-anagrams | |
| 使用长度为26的数组计数, 相同的即在同一组 | |
| ### 94. binary-tree-inorder-traversal | |
| 1. 递归 | |
| 2. 栈：将所有left和left.left先进栈，pop出最新的一个作为当前节点，再切换到当前节点的right | |
| 3. 如果无left,只直接切换到right,否则让root当left的最右子节点的右节点 | |
| ### 144. binary-tree-prorder-traversal | |
| 1. 递归 | |
| 2. 栈：right进栈 | |
| 3. 如果无left,只直接切换到right,否则让right当left的最右子节点的右节点 | |
| ### 590. n-ary-tree-postorder-traversal | |
| 1. 递归 | |
| 2. 栈：先前序后翻转 | |
| ### 589. n-ary-tree-preorder-traversal | |
| 1. 递归 | |
| 2. 栈 | |
| ### 429. n-ary-tree-level-order-traversal | |
| 1. 递归 | |
| 2. 栈 | |
| ### LCOF40. top-k | |
| 1. 大顶堆：取前k个数构建大顶堆，后续元素若小于heap[0],则替换之并shift down | |
| 2. 快速搜索：利用快排思想，当partition==k时即满足条件 | |
| ### 264. ugly-number-ii | |
| 1. 小顶堆：依次弹出堆顶元素，如果之前没有入堆，则加入堆，第n次弹出的元素即为结果 | |
| 2. 三指针：用三个指针依次记录2，3，5因子当前指向的丑数， | |
| ### 347. top-k-frequent-elements | |
| 1. 小顶堆：取前k个数构建小顶堆，后续元素若大于heap[0],则替换之并shift down | |
| 2. 快速搜索：利用快排思想，当partition==k时arr[:k]即结果 | |