如何创建n个数字的平方和的递归方法？

Question

My code must recive n numbers and return the sum of their squares in a recursive method.

Ex: the sum of 1,1,2,2,3 squares must be 19 (1+1+4+4+9)

My code is printing 14 for some reason.

import java.util.Scanner;

/**
 *
 * @author User
 */
public class SomaQuadrados {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) 
    {
      Scanner teclado = new Scanner(System.in);
      int n = teclado.nextInt();
      int numero = 0;
      for(int i = 0; i < n; i++)
      {
           numero = teclado.nextInt();
      }

      System.out.println(somaQuadrados(numero));

    }

    public static int somaQuadrados(int numero)
    {
        if(numero == 0)
        {
            return 0;
        }
        else
        {
            return somaQuadrados(numero-1) + (numero*numero);
        }
    }

}

Answer 1

The problem is your recursive function somaQuadrados() should be processing the list [1, 1, 2, 2, 3] of numbers. That is:

<first number> * <first number> + somaQuadrados(<rest of numbers>)

with base case of an empty list. But instead you're taking an individual number and calculating:

<number> * <number> + somaQuadrados(<number - 1>)

Which is a completely different program. When you process the final element 3 , you get 14 which is 1 * 1 + 2 * 2 + 3 * 3 .

I would expect a solution to this problem to look more like:

import java.util.*;

public class SomaQuadrados {

    public static void main(String[] args) 
    {
        List<Integer> numeros = new ArrayList<>();
        Scanner teclado = new Scanner(System.in);

        while (teclado.hasNextInt()) {
            int numero = teclado.nextInt();
            numeros.add(numero);
        }

        System.out.println(somaQuadrados(numeros));
    }

    public static int somaQuadrados(List<Integer> numeros)
    {
        int size = numeros.size();

        if (size == 0)
        {
            return 0;
        }

        int numero = numeros.get(0);

        return numero * numero + somaQuadrados(numeros.subList(1, size));
    }
}