Grandyang

摘要： 18.4 Write a method to count the number of 2s between 0 and n. 这道题给了我们一个整数n，让我们求[0,n]区间内所有2出现的个数，比如如果n=20，那么满足题意的是2, 12, 20,那么返回3即可。LeetCode上有一道很类似的题F 阅读全文

摘要： 18.3 Write a method to randomly generate a set of m integers from an array of size n. Each element must have equal probability of being chosen. 这道题让我们 阅读全文