Perfect Squares

Source

• leetcode: Perfect Squares

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.

Java

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