[Leetcode445 Stack Solution]Add two numbers, 4 lines

addTwoNumbers.java

/*
 * This code is to describe how to use stack implement adding two numbers.
 * The key is the while-loop in the addTwoNum() method.
 */
import java.util.*;

public class StackNumberApp {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Stack<Integer> s1 = new Stack<>();
		Stack<Integer> s2 = new Stack<>();
		pushNum(22, s1);
		pushNum(99, s2);
		Stack<Integer> s3 = new Stack<>();
		addTwoNum(s1, s2, s3);
		System.out.println(s3.toString());

	}

	private static void addTwoNum(Stack<Integer> s1, Stack<Integer> s2, Stack<Integer> s3) {
		// TODO Auto-generated method stub
		int sum = 0;
		int carry = 0;
		while (!s1.isEmpty() || !s2.isEmpty()||carry!=0) {
			sum = (s1.isEmpty() ? 0 : s1.pop()) + (s2.isEmpty() ? 0 : s2.pop()) + carry;
			s3.push(sum % 10);
			carry = sum / 10;
		}
	}

	public static void pushNum(int num, Stack<Integer> s) {
		Stack<Integer> st = new Stack<>();
		while (num > 0) {
			int t = num % 10;
			st.push(t);
			num = num / 10;
		}
		while (!st.isEmpty()) {
			s.push(st.pop());
		}
	}
}