Perfect Squares

题目描述：

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.

解题思路就是动态规划~

代码如下：

public class Solution {
    public int numSquares(int n) {
        int[] dp=new int[n+1];
        Arrays.fill(dp, Integer.MAX_VALUE);
        for(int i=1;i<=n;i++) {
			if((int)Math.sqrt(i)*(int)Math.sqrt(i)==i){
				dp[i]=1;
			}else{
				for(int j=1;j<=i/2;j++){
					dp[i]=dp[j]+dp[i-j]<dp[i]?dp[j]+dp[i-j]:dp[i];
				}
			}
		}
        return dp[n];
    }
}