题目原文链接见issues 若想按部门/难度/题型筛选题目，可以在CodeTop 查询 题目 出现次数 链接 3. 无重复字符的最长子串 2 https://leetcode-cn.com/problems/longest-substring-without-repeating-characters 146. LRU缓存机制 2 https://leetcode-cn.com/problems/lru-cache 120. 三角形最小路径和 2 https://leetcode-cn.com/problems/triangle 102. 二叉树的层序遍历 2 https://leetcode-cn.com/problems/binary-tree-level-order-traversal 110. 平衡二叉树 2 https://leetcode-cn.com/problems/balanced-binary-tree 200. 岛屿数量 1 https://leetcode-cn.com/problems/number-of-islands 10. 正则表达式匹配 1 https://leetcode-cn.com/problems/regular-expression-matching 129. 求根到叶子节点数字之和 1 https://leetcode-cn.com/problems/sum-root-to-leaf-numbers 227. 基本计算器 II 1 https://leetcode-cn.com/problems/basic-calculator-ii 343. 整数拆分 1 https://leetcode-cn.com/problems/integer-break 215. 数组中的第K个最大元素 1 https://leetcode-cn.com/problems/kth-largest-element-in-an-array 121. 买卖股票的最佳时机 1 https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock 剑指 Offer 53 - II. 0～n-1中缺失的数字 1 https://leetcode-cn.com/problems/que-shi-de-shu-zi-lcof 378. 有序矩阵中第K小的元素 1 https://leetcode-cn.com/problems/kth-smallest-element-in-a-sorted-matrix 8. 字符串转换整数 (atoi) 1 https://leetcode-cn.com/problems/string-to-integer-atoi 486. 预测赢家 1 https://leetcode-cn.com/problems/predict-the-winner 15. 三数之和 1 https://leetcode-cn.com/problems/3sum 781. 森林中的兔子 1 https://leetcode-cn.com/problems/rabbits-in-forest 剑指 Offer 36. 二叉搜索树与双向链表 1 https://leetcode-cn.com/problems/er-cha-sou-suo-shu-yu-shuang-xiang-lian-biao-lcof 46. 全排列 1 https://leetcode-cn.com/problems/permutations 23. 合并K个排序链表 1 https://leetcode-cn.com/problems/merge-k-sorted-lists 460. LFU缓存 1 https://leetcode-cn.com/problems/lfu-cache 2. 两数相加 1 https://leetcode-cn.com/problems/add-two-numbers 4. 寻找两个正序数组的中位数 1 https://leetcode-cn.com/problems/median-of-two-sorted-arrays 611. 有效三角形的个数 1 https://leetcode-cn.com/problems/valid-triangle-number 面试题 08.05. 递归乘法 1 https://leetcode-cn.com/problems/recursive-mulitply-lcci