# 第五章 - 高频考题（中等）

中等题目是力扣比例最大的部分，因此这部分我的题解也是最多的。 大家不要太过追求难题，先把中等难度题目做熟了再说。

这部分的题目要不需要我们挖掘题目的内含信息， 将其抽象成简单题目。 要么是一些写起来比较麻烦的题目， 一些人编码能力不行就挂了。因此大家一定要自己做， 即使看了题解”会了“，也要自己码一遍。自己不亲自写一遍，里面的细节永远不知道。

以下是我列举的经典题目（带 91 字样的表示出自 **91 天学算法**活动）：

* [面试题 17.09. 第 k 个数](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/get-kth-magic-number-lcci)
* [面试题 17.23. 最大黑方阵](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/max-black-square-lcci)🆕
* [0002. 两数相加](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/2.add-two-numbers)
* [0003. 无重复字符的最长子串](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/3.longest-substring-without-repeating-characters)
* [0005. 最长回文子串](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/5.longest-palindromic-substring)
* [0011. 盛最多水的容器](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/11.container-with-most-water)
* [0015. 三数之和](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/15.3sum)
* [0017. 电话号码的字母组合](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/17.letter-combinations-of-a-phone-number)
* [0019. 删除链表的倒数第 N 个节点](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/19.removenthnodefromendoflist)
* [0022. 括号生成](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/22.generate-parentheses)
* [0024. 两两交换链表中的节点](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/24.swapnodesinpairs)
* [0029. 两数相除](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/29.divide-two-integers)
* [0031. 下一个排列](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/31.next-permutation)
* [0033. 搜索旋转排序数组](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/33.search-in-rotated-sorted-array)
* [0039. 组合总和](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/39.combination-sum)
* [0040. 组合总和 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/40.combination-sum-ii)
* [0046. 全排列](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/46.permutations)
* [0047. 全排列 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/47.permutations-ii)
* [0048. 旋转图像](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/48.rotate-image)
* [0049. 字母异位词分组](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/49.group-anagrams)
* [0050. Pow(x, n)](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/50.pow-x-n)
* [0055. 跳跃游戏](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/55.jump-game)
* [0056. 合并区间](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/56.merge-intervals)
* [0060. 第 k 个排列](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/60.permutation-sequence)
* [0061. 旋转链表](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/61.rotate-list) 91
* [0062. 不同路径](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/62.unique-paths)
* [0073. 矩阵置零](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/73.set-matrix-zeroes)
* [0075. 颜色分类](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/75.sort-colors)
* [0078. 子集](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/78.subsets)
* [0079. 单词搜索](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/79.word-search)
* [0080. 删除排序数组中的重复项 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/80.remove-duplicates-from-sorted-array-ii)
* [0086. 分隔链表](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/86.partition-list)
* [0090. 子集 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/90.subsets-ii)
* [0091. 解码方法](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/91.decode-ways)
* [0092. 反转链表 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/92.reverse-linked-list-ii)
* [0094. 二叉树的中序遍历](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/94.binary-tree-inorder-traversal)
* [0095. 不同的二叉搜索树 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/95.unique-binary-search-trees-ii)
* [0096. 不同的二叉搜索树](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/96.unique-binary-search-trees)
* [0098. 验证二叉搜索树](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/98.validate-binary-search-tree)
* [0102. 二叉树的层序遍历](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/102.binary-tree-level-order-traversal)
* [0103. 二叉树的锯齿形层次遍历](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/103.binary-tree-zigzag-level-order-traversal)
* [0113. 路径总和 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/113.path-sum-ii)
* [0129. 求根到叶子节点数字之和](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/129.sum-root-to-leaf-numbers)
* [0130. 被围绕的区域](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/130.surrounded-regions)
* [0131. 分割回文串](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/131.palindrome-partitioning)
* [0139. 单词拆分](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/139.word-break)
* [0144. 二叉树的前序遍历](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/144.binary-tree-preorder-traversal)
* [0147. 对链表进行插入排序](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/147.insertion-sort-list)
* [0150. 逆波兰表达式求值](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/150.evaluate-reverse-polish-notation)
* [0152. 乘积最大子数组](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/152.maximum-product-subarray)
* [0199. 二叉树的右视图](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/199.binary-tree-right-side-view)
* [0200. 岛屿数量](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/200.number-of-islands)
* [0201. 数字范围按位与](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/201.bitwise-and-of-numbers-range)
* [0208. 实现 Trie (前缀树)](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/208.implement-trie-prefix-tree)
* [0209. 长度最小的子数组](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/209.minimum-size-subarray-sum)
* [0211. 添加与搜索单词 \* 数据结构设计](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/211.add-and-search-word-data-structure-design)
* [0215. 数组中的第 K 个最大元素](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/215.kth-largest-element-in-an-array)
* [0221. 最大正方形](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/221.maximal-square)
* [0227. 基本计算器 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/227.basic-calculator-ii)🆕
* [0229. 求众数 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/229.majority-element-ii)
* [0230. 二叉搜索树中第 K 小的元素](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/230.kth-smallest-element-in-a-bst)
* [0236. 二叉树的最近公共祖先](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/236.lowest-common-ancestor-of-a-binary-tree)
* [0238. 除自身以外数组的乘积](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/238.product-of-array-except-self)
* [0240. 搜索二维矩阵 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/240.search-a-2-d-matrix-ii)
* [0279. 完全平方数](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/279.perfect-squares)
* [0309. 最佳买卖股票时机含冷冻期](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/309.best-time-to-buy-and-sell-stock-with-cooldown)
* [0322. 零钱兑换](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/322.coin-change)
* [0328. 奇偶链表](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/328.odd-even-linked-list)
* [0334. 递增的三元子序列](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/334.increasing-triplet-subsequence)
* [0337. 打家劫舍 III](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/337.house-robber-iii)
* [0343. 整数拆分](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/343.integer-break)
* [0365. 水壶问题](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/365.water-and-jug-problem)
* [0378. 有序矩阵中第 K 小的元素](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/378.kth-smallest-element-in-a-sorted-matrix)
* [0380. 常数时间插入、删除和获取随机元素](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/380.insert-delete-getrandom-o1)
* [0394. 字符串解码](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/394.decode-string) 91
* [0416. 分割等和子集](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/416.partition-equal-subset-sum)
* [0445. 两数相加 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/445.add-two-numbers-ii)
* [0454. 四数相加 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/454.4-sum-ii)
* [0464. 我能赢么](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/464.can-i-win)
* [0494. 目标和](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/494.target-sum)
* [0516. 最长回文子序列](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/516.longest-palindromic-subsequence)
* [0513. 找树左下角的值](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/513.find-bottom-left-tree-value) 91
* [0518. 零钱兑换 II](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/518.coin-change-2)
* [0547. 朋友圈](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/broken-reference)
* [0560. 和为 K 的子数组](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/560.subarray-sum-equals-k)
* [0609. 在系统中查找重复文件](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/609.find-duplicate-file-in-system)
* [0611. 有效三角形的个数](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/611.valid-triangle-number)
* [0686. 重复叠加字符串匹配](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/686.repeated-string-match)
* [0718. 最长重复子数组](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/718.maximum-length-of-repeated-subarray)
* [0754. 到达终点数字](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/754.reach-a-number)
* [0785. 判断二分图](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/785.is-graph-bipartite)
* [0816. 模糊坐标](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/816.ambiguous-coordinates)
* [0820. 单词的压缩编码](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/820.short-encoding-of-words)
* [0875. 爱吃香蕉的珂珂](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/875.koko-eating-bananas)
* [0877. 石子游戏](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/877.stone-game)
* [0886. 可能的二分法](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/886.possible-bipartition)
* [0900. RLE 迭代器](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/900.rle-iterator)
* [0911. 在线选举](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/911.online-election)
* [0912. 排序数组](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/912.sort-an-array)
* [0935. 骑士拨号器](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/935.knight-dialer)
* [0978. 最长湍流子数组](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/978.longest-turbulent-subarray)
* [0987. 二叉树的垂序遍历](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/987.vertical-order-traversal-of-a-binary-tree) 91
* [1011. 在 D 天内送达包裹的能力](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1011.capacity-to-ship-packages-within-d-days)
* [1014. 最佳观光组合](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1014.best-sightseeing-pair)
* [1015. 可被 K 整除的最小整数](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1015.smallest-integer-divisible-by-k)
* [1019. 链表中的下一个更大节点](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1019.next-greater-node-in-linked-list)
* [1020. 飞地的数量](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1020.number-of-enclaves)
* [1023. 驼峰式匹配](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1023.camelcase-matching)
* [1031. 两个非重叠子数组的最大和](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1031.maximum-sum-of-two-non-overlapping-subarrays)
* [1104. 二叉树寻路](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1104.path-in-zigzag-labelled-binary-tree)
* [1131.绝对值表达式的最大值](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1131.maximum-of-absolute-value-expression)
* [1186. 删除一次得到子数组最大和](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1186.maximum-subarray-sum-with-one-deletion)
* [1218. 最长定差子序列](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1218.longest-arithmetic-subsequence-of-given-difference)
* [1227. 飞机座位分配概率](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1227.airplane-seat-assignment-probability)
* [1261. 在受污染的二叉树中查找元素](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1261.find-elements-in-a-contaminated-binary-tree)
* [1262. 可被三整除的最大和](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1262.greatest-sum-divisible-by-three)
* [1297. 子串的最大出现次数](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1297.maximum-number-of-occurrences-of-a-substring)
* [1310. 子数组异或查询](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1310.xor-queries-of-a-subarray)
* [1334. 阈值距离内邻居最少的城市](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1334.find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance)
* [1371.每个元音包含偶数次的最长子字符串](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1371.find-the-longest-substring-containing-vowels-in-even-counts)
* [1381. 设计一个支持增量操作的栈](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1381.design-a-stack-with-increment-operation) 91
* [1558. 得到目标数组的最少函数调用次数](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1558.minimum-numbers-of-function-calls-to-make-target-array)
* [1574. 删除最短的子数组使剩余数组有序](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1574.shortest-subarray-to-be-removed-to-make-array-sorted)
* [1631. 最小体力消耗路径](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1631.path-with-minimum-effort)
* [1658. 将 x 减到 0 的最小操作数](https://leetcode-solution-leetcode-pp.gitbook.io/leetcode-solution/medium/1658.minimum-operations-to-reduce-x-to-zero)