Function add

project_euler/problem_13/problem13.go:124–150

(a, b string)

}

func add(a, b string) string {
	if len(a) < len(b) {
		a, b = b, a
	}

	carry := 0
	sum := make([]byte, len(a)+1)

	for i := 0; i < len(a); i++ {
		d := int(a[len(a)-1-i] - '0')
		if i < len(b) {
			d += int(b[len(b)-1-i] - '0')
		}
		d += carry

		sum[len(sum)-1-i] = byte(d%10) + '0'
		carry = d / 10
	}

	if carry > 0 {
		sum[0] = byte(carry) + '0'
	} else {
		sum = sum[1:]
	}

	return string(sum)
}