Envío 4638

Código

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        String num = br.readLine();
        String num2 = br.readLine();
        bw.write(add(num, num2) + "\n");
        br.close();
        bw.close();
    }

    public static String add(String num1, String num2) {
        int N1 = num1.length();
        int N2 = num2.length();
        boolean differentNumberOfDigits = N1 < N2;
        int N = Math.max(N1, N2);
        if (N1 > N2) {
            String temp = num1;
            num1 = num2;
            num2 = temp;
            differentNumberOfDigits = true;
        }
        if (differentNumberOfDigits) {
            int paddingZeros = Math.abs(N1 - N2);
            while (paddingZeros > 0) {
                num1 = '0' + num1;
                paddingZeros--;
            }
        }
        String result = "";
        N1 = N - 1;

        int carry = 0;
        for (int i = 0; i < N; i++) {
            int digit1 = num1.charAt(N1 - i) - '0';
            int digit2 = num2.charAt(N1 - i) - '0';
            int addition = digit1 + digit2 + carry;
            if (addition >= 10 && i < N1) {
                carry = 1;
                addition -= 10;
            } else {
                carry = 0;
            }
            result = addition + result;
        }

        return result;
    }
}