例子：

759+674

1）不考虑进位：   323

2）只考虑进位：1110

3）两者之和：1433 递归求解c

package Hard;

/**

 * Write a function that adds two numbers. You should not use + or any arithmetic operators.

译文：

写一个Add函数求两个数的和，不能使用+号或其它算术运算符。

 *

 */

public class S18_1 {

	public static int add(int a, int b) {

		if (b == 0)

			return a;

		int sum = a ^ b; 				// add without carrying

		int carry = (a & b) << 1; // carry, but don’t add

		return add(sum, carry); // recurse

	}

	public static int randomInt(int n) {

		return (int) (Math.random() * n);

	}

	public static void main(String[] args) {

		for (int i = 0; i < 100; i++) {

			int a = randomInt(10);

			int b = randomInt(10);

			int sum = add(a, b);

			System.out.println(a + " + " + b + " = " + sum);

		}

	}

}