摘要：Give a string s, count the number of non-empty (contiguous) substrings that have the same number of 0's and 1's, and all the 0's and all the 1's in th 阅读全文

摘要：Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array. Example 1: Note: Answer: 这里应用BFS的解法。网上还有一种 阅读全文