371. Sum of Two Integers.java

// https://discuss.leetcode.com/topic/49771/java-simple-easy-understand-solution-with-explanation

// 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;
}

// Iterative
public int getSubtract(int a, int b) {
	while (b != 0) {
		int borrow = (~a) & b;
		a = a ^ b;
		b = borrow << 1;
	}
	
	return a;
}

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

// Recursive
public int getSubtract(int a, int b) {
	return (b == 0) ? a : getSubtract(a ^ b, (~a & b) << 1);
}

// Get negative number
public int negate(int x) {
	return ~x + 1;
}