private void MultiplyRecurive(int index, int count, BigNumber num)
{
for (int i = 1; i <= count; i++) {
if (index == 0) {
if (i != 1) {
AbsoluteAddTo(num);
}
} else {
MultiplyRecurive(index - 1, 10, num);
}
}
}
public void AddTo(BigNumber num)
{
if (num.Sign != this.Sign) {
int compare = num.CompareAbsolute(this);
if (compare < 0) {
AbsoluteSubtractFrom(num, this);
this.Sign = num.Sign;
} else if (compare > 0) {
AbsoluteSubtractFrom(this, num);
this.Digits = num.Digits;
} else {
this.Clear();
this.Sign = enumSign.Positive;
}
} else {
AbsoluteAddTo(num);
}
}
private void BorrowFromNextDigit(BigNumber num, int index)
{
if (num[index] == 0) {
BorrowFromNextDigit(num, index + 1);
num[index] = 9;
} else {
num[index] -= 1;
}
}
private void AbsoluteSubtractFrom(BigNumber from, BigNumber to)
{
for (int index = 0; index < from.Count; index++) {
if (from[index] < to[index]) {
BorrowFromNextDigit(from, index + 1);
from[index] += 10;
}
to[index] = from[index] - to[index];
}
}
private void AbsoluteAddTo(BigNumber from)
{
int carryOver = 0;
int digit = 0;
while (digit < from.Count || carryOver > 0) {
int sum = 0;
if (digit < from.Count) {
sum = from[digit] + this[digit] + carryOver;
} else {
sum = this[digit] + carryOver;
}
if (sum > 9) {
string sumText = sum.ToString();
this[digit] = Convert.ToInt32(sumText.Substring(1, 1));
carryOver = Convert.ToInt32(sumText.Substring(0, 1));
} else {
this[digit] = sum;
carryOver = 0;
}
digit++;
}
}
public void MultiplyBy(BigNumber num)
{
BigNumber thisOriginal = new BigNumber();
thisOriginal.Digits = this.Digits;
for (int index = 0; index < num.Count; index++) {
if (num[index] > 0) {
MultiplyRecurive(index, num[index], thisOriginal);
}
}
if (num.Sign != this.Sign) {
this.Sign = enumSign.Negative;
} else if (this.Sign == enumSign.Negative) {
this.Sign = enumSign.Positive;
}
}
public int CompareAbsolute(BigNumber num)
{
for (int index = Math.Max(this.Count, num.Count); index >= 0; index--) {
if (num[index] > this[index]) {
return 1;
} else if (num[index] < this[index]) {
return -1;
}
}
return 0;
}