static void PrintAllOperations(StringBigInteger a, StringBigInteger b)
{
// PrintAdd(a, b);
// PrintSubtract(a, b);
// PrintSubtract(b, a);
PrintMultiply(a, b);
}
public static StringBigInteger FullKWrapper(StringBigInteger a, StringBigInteger b)
{
var isNegative = a._isNegative ^ b._isNegative;
var posA = a._isNegative ? FlipSign(a) : a;
var posB = b._isNegative ? FlipSign(b) : b;
var result = KMultiply(a, b);
return(isNegative ? FlipSign(result) : result);
}
private static StringBigInteger MultiplyByTens(StringBigInteger ac, int n)
{
if (ac._value == "0")
{
return(ac);
}
var value = ac._value.PadRight(n + ac.Length, '0');
return(new StringBigInteger(value));
}
private static StringBigInteger Bottom(StringBigInteger x, int n_2, int n)
{
var m = n_2 - (n - x.Length);
if (m == 0)
{
return(x);
}
if (m >= x.Length)
{
return(new StringBigInteger("0"));
}
return(new StringBigInteger(x._value.Substring(m)));
}
public static StringBigInteger KMultiply(StringBigInteger x, StringBigInteger y)
{
if (x._value == "0" || y._value == "0")
{
return(new StringBigInteger("0"));
}
if (x._value == "1")
{
return(y);
}
if (y._value == "1")
{
return(x);
}
if (x.Length == 1 && y.Length == 1)
{
return(SingleDigitMultiply(x, y));
}
var compare = CompareIgnoreSign(x, y);
var bigger = compare >= 0 ? x : y;
var smaller = compare >= 0 ? y : x;
var n = bigger.Length;
var n_2 = n / 2;
var a = Top(bigger, n_2, n);
var b = Bottom(bigger, n_2, n);
var c = Top(smaller, n_2, n);
var d = Bottom(smaller, n_2, n);
var ac = KMultiply(a, c);
var bd = KMultiply(b, d);
var ad = KMultiply(a, d);
var bc = KMultiply(b, c);
//note - this is not really doing karatsuba, because it's not doing the proper calculation that avoids 4 recursive calls
//solving that problem requires modifying the algorithm to correctly handle multiplication of two numbers
//with different numbers of digits
var ad_bc = ad + bc; // KMultiply(a + b, c + d) - ac - bd;
var ac_n = MultiplyByTens(ac, n);
var ad_bc_n_2 = MultiplyByTens(ad_bc, n_2);
var result = ac_n + ad_bc_n_2 + bd;
return(result);
}
private static int CompareIgnoreSign(StringBigInteger a, StringBigInteger b)
{
if (a._value.Length > b._value.Length)
{
return(1);
}
if (a._value.Length < b._value.Length)
{
return(-1);
}
for (int i = 0; i < a._value.Length; i++)
{
var compare = a._value[i] - b._value[i];
if (compare != 0)
{
return(compare);
}
}
return(0);
}
static void Main(string[] args)
{
var c = new StringBigInteger("100");
var d = new StringBigInteger("100");
PrintAllOperations(c, d);
var a = new StringBigInteger("54");
var b = new StringBigInteger("12");
PrintAllOperations(a, b);
var a0 = new StringBigInteger("5454");
var b0 = new StringBigInteger("1212");
PrintAllOperations(a0, b0);
// var a1 = new StringBigInteger("321");
// var b1 = new StringBigInteger("345");
// PrintAllOperations(a1, b1);
// var a2 = new StringBigInteger("54321");
// var b2 = new StringBigInteger("12345");
// PrintAllOperations(a2, b2);
// var a3 = new StringBigInteger("1234");
// var b3 = new StringBigInteger("321");
// PrintAllOperations(a3, b3);
// var a4 = new StringBigInteger("1234");
// var b4 = new StringBigInteger("123");
// PrintAllOperations(a4, b4);
// var a5 = new StringBigInteger("3141592653589793238462643383279502884197169399375105820974944592");
// var b5 = new StringBigInteger("2718281828459045235360287471352662497757247093699959574966967627");
// PrintAllOperations(a5, b5);
}
private static StringBigInteger Add(StringBigInteger a, StringBigInteger b)
{
bool sameSign = a._isNegative == b._isNegative;
var compare = CompareIgnoreSign(a, b);
var aIsSmaller = compare < 0;
var bigger = aIsSmaller ? b : a;
var smaller = aIsSmaller ? a : b;
if (sameSign)
{
var addResult = AddStrings(bigger._value, smaller._value);
return(new StringBigInteger(addResult, a._isNegative));
}
else if (compare == 0 && b._isNegative)
{
return(new StringBigInteger("0"));
}
else
{
var isNegative = aIsSmaller == b._isNegative;
string addResult = AddStrings(bigger._value, smaller._value, true);
return(new StringBigInteger(addResult, isNegative));
}
}
private static StringBigInteger SingleDigitMultiply(StringBigInteger x, StringBigInteger y) => new StringBigInteger(((x._value[0] - '0') * (y._value[0] - '0')).ToString());
public static StringBigInteger FlipSign(StringBigInteger value) => new StringBigInteger(value._value, !value._isNegative);
private static void PrintMultiply(StringBigInteger a, StringBigInteger b)
{
Console.WriteLine($"{a} * {b} = {a * b}");
}
static void PrintSubtract(StringBigInteger a, StringBigInteger b)
{
Console.WriteLine($"{a} - {b} = {a - b}");
}
static void PrintAdd(StringBigInteger a, StringBigInteger b)
{
Console.WriteLine($"{a} + {b} = {a + b}");
}