Add 2 Binary Strings #go

addBinary.go

/*
 Observation: We start from the last char for each string. As long as we have not reached the beginning we compare the chars. The math is
 1 + 1 = 0 (curry = 1)
 1 + 0 = 0 + 1 = 1 (curry = 0)
 
 1 + 1 = 1 (curry = 1) if curry = 1
 1 + 0 = 0 + 1 = 0 (curry = 1) if curry = 1
 
 If we have a curry in the end we prepend the 1
 
 Note: Adding 2 mumbers is similar. We have to calculate:
 sum := carry + x + y
 carry = sum / 10
 val = sum % 10
 
*/ 

func AddBinary(a string, b string) string {
	res := ""
	curry := 0
	l1 := len(a) - 1
	l2 := len(b) - 1
	for l1 >= 0 || l2 >= 0 {
		var left = 0
		var right = 0
		if l1 >= 0 {
			if rune(a[l1]) == '1' {
				left = 1
			}
			l1 -= 1
		}
		if l2 >= 0 {
			if rune(b[l2]) == '1' {
				right = 1
			}
			l2 -= 1
		}
		added := curry + left + right
		switch added {
		case 0:
			res = "0" + res
			curry = 0
		case 1:
			res = "1" + res
			curry = 0
		case 2:
			res = "0" + res
			curry = 1
		case 3:
			res = "1" + res
			curry = 1
		}
	}

	if curry == 1 {
		res = "1" + res
	}
	return res
}