题目 Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, -) which sum to n. For example, given n = 12, return 3 because 12 = 4 + 4 + 4; given n = 13, return 2 because 13 = 4 + 9. 分析 完美平方数,给定任意数n,它可表示为多…