Leetcode:279Perfect Squares

 题目出处：Leetcode:279Perfect 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

.

翻译很简单，此处不再赘述。

这是一个dp问题（动态规划问题）动态公式：dp[i + j * j] = min(dp[i] + 1,dp[i + j * j ]);

已通过系统的代码：

public class Solution {
public int numSquares(int n) {
int[] squ = new int[n + 1];
for(int i = 1;i*i <=n ; i++)
squ[i*i] = 1;
for(int j = 1,k = 1; j + k * k <= n;j++){
for(;j + k * k <= n;k++){
if((squ[j + k * k] == 0)||squ[j+k*k]>(squ[j]+1))
squ[j + k * k] = squ[j] + 1;
}
k = 1;
}
return squ
;
}
}