백준 11726번(Java)

import java.io.*;

public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		
		int n = Integer.parseInt(br.readLine());
		int dp[] = new int[n+1];
		
		dp[0] = 0;
		dp[1] = 1;
		
		for(int i=2; i<=n; i++) {
			dp[i] = dp[i-1];
			
			for(int j=1; j*j<=i; j++) {
				dp[i] = Math.min(dp[i], dp[i-(j*j)]);
			}
			
			dp[i]++;
		}
		System.out.println(dp[n]);
	}
}