Given a string S and a string T, count the number of distinct subsequences of T in S. A subsequence of a strin…

典型的hashMap 解决方法 class Solution { func twoSum(_ nums: [Int], _ target: Int) -> [Int] { var dic = [Int: Int](…

什么是好代码 好的代码是自解释的, 好的变量名, 好的结构. 后来复习解法 后来解法没有刚开始的时候解法简单. 尤其是使用 OBSTACLE_FLAG 替换掉magic number是一个好办法. class Solut…

Given a string S and a string T, find the minimum window in S which will contain all the characters in T in co…

53. Maximum Subarray 题目 Find the contiguous subarray within an array (containing at least one number) which ha…

  Given an array of integers, find out whether there are two distinct indices i and j in the array such t…

  Your are given an array of integers prices, for which the i-th element is the price of a give…

题目： Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree i…

思路 插入排序，维持两个链表，第一个原始链表，第二个排好序的链表。为了操作方便，第二个链表设置一个哑元dummy。当原始链表为空或者只有一个元素时，直接返回。如果不是，初始化dummy链表。每次从第一个链表中拿出一个元素…

题目 Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left lea…

题目 Given a sorted array and a target value, return the index if the target is found. If not, return the index …

题目 Given an array of integers nums, write a method that returns the “pivot” index of this array. W…