leetcode 279. Perfect Squares 类似背包问题 + 很简单的动态规划DP解决
Givenapositiveintegern,findtheleastnumberofperfectsquarenumbers(forexample,1,4,9,16,…)whichsumton.Forexample,givenn=12,return3because12=4+4+4;givenn=13,return2because13=4+9.动态规划用dp[i]数组存储第i个数的完美平方数。递推