11448 accepted.cpp

//not so efficient
#include <bits/stdc++.h>
using namespace std;

struct Bigint{
    string a;
    int sign;
    Bigint(){}
    Bigint(string b){(*this) = b;}
    int size(){
        return a.size();
    }
    Bigint inverseSign(){
    sign*= -1;
    return (*this);
    }
    Bigint normalize(int newSign){
        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);
    }
    void operator = (string b){
        a = b[0] == '-' ? b.substr(1) : b;
        reverse(a.begin(), a.end() );
        this->normalize(b[0] == '-' ? -1 : 1);
    }
    bool operator < (const Bigint &b) const {
        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 {
        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('-');
        if(a.empty())
            putchar('0');
        else{
            for( int i = a.size() - 1; i >= 0; i-- )
                putchar(a[i]);
        }
    }
};

int main()
{
    Bigint a,b,c;
    string input;
    int n;
    cin>>n;
    for(int i=0 ; i<n ; i++){
        cin>>input;
        a=input;
        cin>>input;
        b=input;

        c = a - b;
        c.print();
        printf("\n");
    }
    return 0;
}