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N043MultiplyStr.go
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175 lines (162 loc) · 3.61 KB
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package main
type Number struct {
m_digits []byte
m_isPositive bool
m_dotIndex int // From the end. E.g. dotIndex of 2.5 is -1. If digits are 25 and dotIndex is 1, the actual number is 250
}
// vector multiplies a single digit
func (this *Number) multiplyDigit(vec *[]byte, digit byte) {
size := len(*vec)
var multi, adv byte
for i := size - 1; i >= 0; i-- {
multi = (*vec)[i]*digit + adv
(*vec)[i] = multi % 10
adv = multi / 10
}
if adv > 0 {
tmp := make([]byte, size+1)
tmp[0] = byte(adv)
for i, size := 0, len(*vec); i < size; i++ {
tmp[1+i] = (*vec)[i]
}
*vec = tmp
}
}
// vector adds another vector
// vec1 is longer than vec2
func (this *Number) addDigits(pvec1 *[]byte, vec2 []byte) {
vec1 := *pvec1
size1 := len(vec1)
size2 := len(vec2)
i := 0
var adv byte
for ; i < size2; i++ {
c1 := vec1[size1-i-1] + vec2[size2-i-1] + adv
vec1[size1-i-1] = c1 % 10
adv = c1 / 10
}
for ; i < size1; i++ {
c1 := vec1[size1-i-1] + adv
vec1[size1-i-1] = c1 % 10
adv = c1 / 10
}
if adv > 0 {
tmp := make([]byte, len(vec1)+1)
tmp[0] = adv
for i, size := 0, len(vec1); i < size; i++ {
tmp[1+i] = vec1[i]
}
*pvec1 = tmp
}
}
func (this *Number) Init(num string) {
this.m_isPositive = true
this.m_dotIndex = 0
length := len(num)
if length == 0 {
return
}
tempDot := -1
var c byte
for i := 0; i < length; i++ {
c = num[i]
if c == '+' {
this.m_isPositive = true
} else if c == '-' {
this.m_isPositive = false
} else if c == '.' {
tempDot = i
} else {
this.m_digits = append(this.m_digits, c-'0')
}
}
if tempDot >= 0 {
this.m_dotIndex = tempDot + 1 - length
}
// Remove leading 0
leading0Count := 0
for i := range this.m_digits {
if this.m_digits[i] == 0 {
leading0Count++
} else {
break
}
}
this.m_digits = this.m_digits[leading0Count:]
}
func (this *Number) multiply(pother *Number) {
other := *pother
if (this.m_isPositive == true && other.m_isPositive == true) ||
(this.m_isPositive == false && other.m_isPositive == false) {
this.m_isPositive = true
} else {
this.m_isPositive = false
}
lengthOther := len(other.m_digits)
if lengthOther == 0 || len(this.m_digits) == 0 {
this.m_digits = this.m_digits[:0]
this.m_dotIndex = 0
return
}
copydigits := make([]byte, len(this.m_digits))
copy(copydigits, this.m_digits)
for i := 0; i < lengthOther; i++ {
if i == 0 {
this.multiplyDigit(&this.m_digits, other.m_digits[i])
} else {
this.m_digits = append(this.m_digits, 0)
temp := make([]byte, len(copydigits))
copy(temp, copydigits)
this.multiplyDigit(&temp, other.m_digits[i])
this.addDigits(&this.m_digits, temp)
}
}
this.m_dotIndex += other.m_dotIndex
}
func (this *Number) toString() string {
str := make([]byte, 0)
// Sign
if !this.m_isPositive {
str = append(str, '-')
}
// Digits and dot
length := len(this.m_digits)
if length == 0 {
str = append(str, '0')
return string(str)
}
if length == -this.m_dotIndex {
str = append(str, '0')
}
for i := 0; i < length; i++ {
if i == length+this.m_dotIndex {
// if the remaining digits are all 0, need not add dot
allZero := true
for j := i; j < length; j++ {
if this.m_digits[j] != 0 {
allZero = false
break
}
}
if allZero {
break
}
str = append(str, '.')
}
str = append(str, this.m_digits[i]+'0')
}
// Append possible '0's
for i := 0; i < this.m_dotIndex; i++ {
str = append(str, '0')
}
return string(str)
}
type N043MultiplyStr struct {
}
func (this *N043MultiplyStr) multiply(num1 string, num2 string) string {
var n1, n2 Number
n1.Init(num1)
n2.Init(num2)
n1.multiply(&n2)
return n1.toString()
}