摘要： 原题链接在这里：https://leetcode.com/problems/first-unique-character-in-a-string/ 题目： Given a string, find the first non-repeating character in it and return 阅读全文

摘要： 原题链接在这里：https://leetcode.com/problems/sum-of-left-leaves/ 题目： Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 The 阅读全文