[leetCode刷题笔记]371. Sum of Two Integers

原创于 2017-06-11 23:53:32 发布 · 266 阅读

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本文详细介绍了位运算的基本概念及操作符，包括AND、XOR、NOT运算，并通过实例展示了这些运算的应用。此外，还提供了两种不同的Java实现方法来求两个整数之和，不使用加号或减号，而是利用位运算。

对bit运算实在不了解

"&" AND operation, for example, 2 (0010) & 7 (0111) => 2 (0010)

"^" XOR operation, for example, 2 (0010) ^ 7 (0111) => 5 (0101)

"~" NOT operation, for example, ~2(0010) => -3 (1101) what??? Don't get frustrated here. It's called two's complement.

public class Solution {
    public int getSum(int a, int b) {
        return (b == 0) ? a : getSum(a ^ b, (a & b) << 1);
    }
}

// Iterative
public int getSum(int a, int b) {
	if (a == 0) return b;
	if (b == 0) return a;

	while (b != 0) {
		int carry = a & b;
		a = a ^ b;
		b = carry << 1;
	}
	
	return a;
}