In C++, the largest int value is 2147483647. So, an integer larger than this can
ID: 3633036 • Letter: I
Question
In C++, the largest int value is 2147483647.So, an integer larger than this cannot be stored and processed as an integer.
Similarly, if the sum or product of two positive integers is greater than
2147483647, the result will be incorrect. One way to store and manipulate
large integers is to store each individual digit of the number in an array.
Write a program that inputs two positive integers of, at most, 20 digits and
outputs the sum of the numbers. If the sum of the numbers has more than
20 digits, output the sum with an appropriate message. Your program must, at least, contain a function to read and store a number into an array and
another function to output the sum of the numbers.
Explanation / Answer
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#include <iostream>
#include <cctype>
#include <cstring>
using namespace std;
#define DIGITS 20
class largeintegers
{
public:
largeintegers();
void Input();
void Output();
largeintegers operator+( largeintegers );
largeintegers operator-( largeintegers );
largeintegers operator*( largeintegers );
int operator==( largeintegers);
private:
int integer[ DIGITS ];
int len;
};
void largeintegers::Output()
{
int i;
for (i=len-1;i >= 0; i-- )
cout<<integer[i];
}
void largeintegers::Input()
{string in;
int i,j,k;
cout<<"Enter a number("<<DIGITS<<" digits max):";
cin>>in;
for(i=0;in[i]!='';i++);
len=i;
k=0;
for(j=i-1;j>=0;j--)
integer[j]=in[k++]-48;
}
largeintegers::largeintegers( )
{
for ( int i = 0; i <DIGITS; i++ )
integer[ i ] = 0;
len=DIGITS-1;
}
int largeintegers::operator==( largeintegers op2 )
{int i;
if(len<op2.len)
return -1;
if(op2.len<len)
return 1;
for(i=len-1;i>=0;i--)
if(integer[i]<op2.integer[i])
return -1;
else if(op2.integer[i]<integer[i])
return 1;
return 0;
}
largeintegers largeintegers::operator+( largeintegers op2 )
{largeintegers temp;
int carry = 0;
int c,i;
if(len>op2.len)
c=len;
else
c=op2.len;
for ( i=0; i<c; i++ )
{temp.integer[ i ] =integer[ i ] + op2.integer[ i ] + carry;
if ( temp.integer[ i ] > 9 )
{temp.integer[ i ] %= 10;
carry = 1;
}
else
carry = 0;
}
if(carry==1)
{temp.len=c+1;
if(temp.len>=DIGITS)
cout<<"***OVERFLOW***** ";
else
temp.integer[i]=carry;
}
else
temp.len=c;
return temp;
}
largeintegers largeintegers::operator-( largeintegers op2 )
{largeintegers temp;
int c;
if(len>op2.len)
c=len;
else
c=op2.len;
int borrow = 0;
for( int i = c;i >= 0;i--)
if(borrow==0)
{if(integer[i]>=op2.integer[i])
temp.integer[i]=integer[i]-op2.integer[i];
else
{borrow=1;
temp.integer[i]=integer[i]+10-op2.integer[i];
}
}
else
{borrow=0;
if(integer[i]-1>=op2.integer[i])
temp.integer[i]=integer[i]-1-op2.integer[i];
else
{borrow=1;
temp.integer[i]=integer[i]-1+10-op2.integer[i];
}
}
temp.len=c;
return temp;
}
largeintegers largeintegers::operator*( largeintegers op2 )
{ largeintegers temp;
int i,j,k,tmp,m=0;
for (int i=0; i<op2.len; i++)
{ k=i;
for (j=0; j< len; j++)
{tmp = integer[ j ] * op2.integer[i];
temp.integer[k] =temp.integer[k]+tmp;
temp.integer[k+1] =temp.integer[k+1]+ temp.integer[k]/10;
temp.integer[k] %=10;
k++;
if(k>m)
m=k;
}
}
temp.len=m;
if(temp.len>DIGITS)
cout<<"***OVERFLOW***** ";
return temp;
}
using namespace std;
int main()
{int c;
largeintegers n1,n2,result;
n1.Input();
n2.Input();
n1.Output();
cout <<" + ";
n2.Output();
result=n1+n2;
cout<< " = " ;
result.Output();
cout << " ";
n1.Output();
cout <<" - ";
n2.Output();
result=n1-n2;
cout<< " = " ;
result.Output();
cout << " ";
n1.Output();
cout <<" * ";
n2.Output();
result=n1*n2;
cout<< " = " ;
result.Output();
cout << " ";
c=n1==n2;
n1.Output();
switch (c)
{case -1: cout<<" is less than ";
break;
case 0: cout<<" is equal to ";
break;
case 1: cout<<" is greater than ";
break;
}
n2.Output();
cout << " ";
system("pause");
}