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Karatsuba.java
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Karatsuba.java
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import java.util.Arrays;
import java.util.Scanner;
class Karatsuba
{
public int[] Multiply_Base(int[]a, int power){
int[] a2=new int[a.length+power];
for(int i=0;i<a.length;i++)
a2[i]=a[i];
return a2;
}
public int[] Equal(int[]a,int[]b){
int diff=a.length-b.length;
int[] b2=new int[a.length];
for(int i=diff;i<a.length;i++)
b2[i]=b[i-diff];
return b2;
}
public static int Maximum(int a, int b){
if(a>b)
return a;
else
return b;
}
int[] Add(int[] a, int[]b)
{
if(a.length>b.length)
b=Equal(a,b);
if(a.length<b.length)
a=Equal(b,a);
int[] result=new int[a.length+1];
for(int i=result.length-1;i>=1;i--){
result[i]+=a[i-1]+b[i-1];
if(result[i]>=10){
result[i-1]+=result[i]/10;
result[i]=result[i]%10;
}
}
int temp=0;
while(temp<result.length && result[temp]==0 ){
temp++;
}
if(temp!=0){
int[] result2=new int[result.length-temp];
for(int i=0;i<result2.length;i++)
result2[i]=result[i+temp];
return result2;
}
return result;
}
public int[] Substract(int[] a, int[]b){
if(a.length>b.length){
b=Equal(a,b);
}
int sub=0;
int carry =0;
int[] result=new int[a.length];
for(int i=a.length-1;i>=0;i--){
sub=a[i]-b[i]-carry;
carry=0;
if(sub<0){
carry=1;
sub+=10;
}
result[i]=sub;
}
int temp=0;
while(temp<result.length && result[temp]==0 ){
temp++;
}
if(temp!=0){
int[] result2=new int[result.length-temp];
for(int i=0;i<result2.length;i++)
result2[i]=result[i+temp];
return result2;
}
return result;
}
public int[] SubArray(int[]a,int start,int end){
int[] result=new int[end-start+1];
for(int i=0,j=start;i<result.length && j<=end;i++,j++){
result[i]=a[j];
}
return result;
}
public int[] Multiplication(int[] a,int[] b){
if(a.length>b.length)
b=Equal(a,b);
if(a.length<b.length)
a=Equal(b,a);
if(a.length==1 && b.length==1){
int product=a[0]*b[0];
if(product>=10){
int[] result=new int[2];
result[0]=product/10;
result[1]=product%10;
return result;
}
else{
int[] result=new int[1];
result[0]=product;
return result;
}
}
else{
int n=a.length;
int m=n/2;
int[] al=SubArray(a, 0, n-m-1);
int[] ar=SubArray(a, n-m,a.length-1);
int[] bl=SubArray(b, 0, n-m-1);
int[] br=SubArray(b, n-m, a.length-1);
int[] z2=Multiplication(al, bl);
int[] z0=Multiplication(ar, br);
int[] z1=Substract(Substract(Multiplication(Add(al,ar),Add(bl,br)),z2),z0);
return Add(Add(Multiply_Base(z2, 2*m),Multiply_Base(z1,m)),z0);
}
}
public static void main(String[]args)
{
Scanner sc=new Scanner(System.in);
System.out.println("Enter first number");
String A= sc.nextLine();
System.out.println("\nEnter Second number:");
String B=sc.nextLine();
int [] a=new int[A.length()];
int [] b=new int[B.length()];
for(int j=0;j<A.length();j++)
{
a[j]=Character.getNumericValue(A.charAt(j));
}
for(int j=0;j<B.length();j++)
{
b[j]=Character.getNumericValue(B.charAt(j));
}
Karatsuba r1=new Karatsuba();
/*
if(a.length>b.length)
b=r1.Equal(a,b);
if(a.length<b.length)
a=r1.Equal(b,a); */
int[] result=r1.Multiplication(a,b);
System.out.println();
for(int j=0;j<result.length;j++)
{
System.out.print(result[j]);
}
}
}