LeetCode六月挑战（6.27 ）Perfect Squares LeetCode 279解题方案

LeetCode六月挑战（6.27 ）Perfect Squares LeetCode 279解题方案

Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, …) which sum to n.

Example 1:

Input: n = 12
Output: 3 
Explanation: 12 = 4 + 4 + 4.
Example 2:

Input: n = 13
Output: 2
Explanation: 13 = 4 + 9.

思路

动态规划问题，每一个数可以看成一个完美平方数加一个普通数

代码

public class Solution {
    public int numSquares(int n) {
        int[] dp = new int[n+1];
        Arrays.fill(dp, Integer.MAX_VALUE);
        for(int i = 0; i * i <= n; i++) 
            dp[i * i] = 1;
        for(int i = 1; i <= n; i++)   
            for(int j = 1; i + j * j <= n; j++)   
                dp[i + j * j] = Math.min(dp[i] + 1, dp[i + j * j]); 
        return dp[n];
    }
}