Added library of Big Integers for C++

libraries/Bigint.cpp

@@ -0,0 +1,156 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+/*
+  Big Integer Library
+  by
+  Jane Alam Jan
+*/
+struct Bigint {
+  // representations and structures
+  string a; // to store the digits
+  int sign; // sign = -1 for negative numbers, sign = 1 otherwise
+
+  // constructors
+  Bigint() {} // default constructor
+  Bigint( string b ) { (*this) = b; } // constructor for string
+
+  // some helpful methods
+  int size() { // returns number of digits
+    return a.size();
+  }
+
+  Bigint inverseSign() { // changes the sign
+    sign *= -1;
+    return (*this);
+  }
+
+  Bigint normalize( int newSign ) { // removes leading 0, fixes sign
+    for( int i = a.size() - 1; i > 0 && a[i] == '0'; i-- )
+      a.erase(a.begin() + i);
+    sign = ( a.size() == 1 && a[0] == '0' ) ? 1 : newSign;
+    return (*this);
+  }
+
+  // assignment operator
+  void operator = ( string b ) { // assigns a string to Bigint
+    a = b[0] == '-' ? b.substr(1) : b;
+    reverse( a.begin(), a.end() );
+    this->normalize( b[0] == '-' ? -1 : 1 );
+  }
+
+
+  // conditional operators
+  bool operator < ( const Bigint &b ) const { // less than operator
+    if( sign != b.sign ) return sign < b.sign;
+    if( a.size() != b.a.size() )
+      return sign == 1 ? a.size() < b.a.size() : a.size() > b.a.size();
+    for( int i = a.size() - 1; i >= 0; i-- ) if( a[i] != b.a[i] )
+      return sign == 1 ? a[i] < b.a[i] : a[i] > b.a[i];
+    return false;
+  }
+
+  bool operator == ( const Bigint &b ) const { // operator for equality
+    return a == b.a && sign == b.sign;
+  }
+
+
+  // mathematical operators
+  Bigint operator + ( Bigint b ) { // addition operator overloading
+    if( sign != b.sign ) return (*this) - b.inverseSign();
+    Bigint c;
+    for(int i = 0, carry = 0; i<a.size() || i<b.size() || carry; i++ ) {
+      carry+=(i<a.size() ? a[i]-48 : 0)+(i<b.a.size() ? b.a[i]-48 : 0);
+      c.a += (carry % 10 + 48);
+      carry /= 10;
+    }
+
+    return c.normalize(sign);
+  }
+
+  Bigint operator - ( Bigint b ) { // subtraction operator overloading
+    if( sign != b.sign ) return (*this) + b.inverseSign();
+    int s = sign; sign = b.sign = 1;
+    if( (*this) < b ) return ((b - (*this)).inverseSign()).normalize(-s);
+
+    Bigint c;
+    for( int i = 0, borrow = 0; i < a.size(); i++ ) {
+      borrow = a[i] - borrow - (i < b.size() ? b.a[i] : 48);
+      c.a += borrow >= 0 ? borrow + 48 : borrow + 58;
+      borrow = borrow >= 0 ? 0 : 1;
+    }
+
+    return c.normalize(s);
+  }
+
+  Bigint operator * ( Bigint b ) { // multiplication operator overloading
+    Bigint c("0");
+    for( int i = 0, k = a[i] - 48; i < a.size(); i++, k = a[i] - 48 ) {
+      while(k--) c = c + b; // ith digit is k, so, we add k times
+      b.a.insert(b.a.begin(), '0'); // multiplied by 10
+    }
+
+    return c.normalize(sign * b.sign);
+  }
+
+  Bigint operator / ( Bigint b ) { // division operator overloading
+    if( b.size() == 1 && b.a[0] == '0' ) b.a[0] /= ( b.a[0] - 48 );
+
+    Bigint c("0"), d;
+    for( int j = 0; j < a.size(); j++ ) d.a += "0";
+
+    int dSign = sign * b.sign; b.sign = 1;
+    for( int i = a.size() - 1; i >= 0; i-- ) {
+      c.a.insert( c.a.begin(), '0');
+      c = c + a.substr( i, 1 );
+      while( !( c < b ) ) c = c - b, d.a[i]++;
+    }
+
+    return d.normalize(dSign);
+  }
+
+  Bigint operator % ( Bigint b ) { // modulo operator overloading
+    if( b.size() == 1 && b.a[0] == '0' ) b.a[0] /= ( b.a[0] - 48 );
+
+    Bigint c("0");
+    b.sign = 1;
+    for( int i = a.size() - 1; i >= 0; i-- ) {
+      c.a.insert( c.a.begin(), '0');
+      c = c + a.substr( i, 1 );
+      while( !( c < b ) ) c = c - b;
+    }
+
+    return c.normalize(sign);
+  }
+
+  // output method
+  void print() {
+    if( sign == -1 ) putchar('-');
+    for( int i = a.size() - 1; i >= 0; i-- ) putchar(a[i]);
+  }
+};
+
+int main() {
+  Bigint a, b;
+  a = "9999999999999999999999999999999999999999";
+  b = "1";
+
+  Bigint sum = a + b;
+  sum.print();
+  cout << endl;
+
+  Bigint div = sum / (a + b);
+  div.print();
+  cout << endl;
+
+  Bigint sub = sum - sum;
+  sub.print();
+  cout << endl;
+
+  Bigint mul = (sum * sum) - b;
+  mul.print();
+  cout << endl;
+
+
+  return 0;
+}