Fast_I\O.txt

Methods
1.   using scanf() , printf() is faster than cin, cout.
2.   you can still use cin/cout and achieve the same speed as scanf/printf by including the following two lines in your main() function:

        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        
    It toggles on or off the synchronization of all the C++ standard streams with their corresponding standard C streams 
    if it is called before the program performs its first input or output operation.
    Adding ios_base::sync_with_stdio (false); (which is true by default) before any I/O operation avoids this synchronization.
    It is a static member of function of std::ios_base.    
    
    tie() is a method which simply guarantees the flushing of std::cout before std::cin accepts an input. This is useful for interactive
    console programs which require the console to be updated constantly but also slows down the program for large I/O. The NULL part just
    returns a NULL pointer.
    
    #include <bits/stdc++.h>
    using namespace std;

    int main()
    {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int a;
    cin>> a;
    cout<< a<<"\n";  //use "\n" instead of endl because endl forces a flushing stream, which is usually unnecessary
    return 0;
   }
   
   
3.  For Higher Competative programmings : (ACM ICPC, Google CodeJam, TopCoder Open, )
    SOURCE:  http://www.geeksforgeeks.org/fast-io-for-competitive-programming/
    
    void fastscan(int &number)
    {
    //variable to indicate sign of input number
    bool negative = false;
    register int c;
 
    number = 0;
 
    // extract current character from buffer
    c = getchar();
    if (c=='-')
    {
        // number is negative
        negative = true;
 
        // extract the next character from the buffer
        c = getchar();
    }
 
    // Keep on extracting characters if they are integers
    // i.e ASCII Value lies from '0'(48) to '9' (57)
    for (; (c>47 && c<58); c=getchar())
        number = number *10 + c - 48;
 
    // if scanned input has a negative sign, negate the
    // value of the input number
    if (negative)
        number *= -1;
    }
 
   // Function Call
     int main()
    {
    int number;
    fastscan(number);
    cout << number << "\n";
    return 0;
    }
 
 
4.  Using getchar_unlocked() :
     http://www.geeksforgeeks.org/getchar_unlocked-faster-input-cc-competitive-programming/