xinyu04

摘要： Suppose you have a coin in which the probability of flipping a heads is $p$, where $p\ge0.5$ . What is the expected number of flips it will take for t 阅读全文

摘要： Show that any prime number other than 2 can be expressed as the difference of two squares, where each square is an integer squared. Solution 任何质数都是奇数。 阅读全文

摘要： How many subsquares can you form on chessboard with $n*n$ unit squares? Subsquares must be an integer squared. Solution 很明显的方法就是枚举正方形的边长，然后统计该边长的正方形的个 阅读全文

摘要： Given a list of 24-hour clock time points in "HH:MM" format, return the minimum minutes difference between any two time-points in the list. Solution 这 阅读全文

摘要： You are given an m x n binary matrix grid. In one operation, you can choose any row or column and flip each value in that row or column (i.e., changin 阅读全文