C++ unordered_map

It is a special map, the key query complexity is O (1), but the map for keys complexity is O (log N)

Some compiler to add the following header file when using:

#if(__cplusplus == 201103L)
#include <unordered_map>
#include <unordered_set>
#else
#include <tr1/unordered_map>
#include <tr1/unordered_set>
namespace std
{
    using std::tr1::unordered_map;
    using std::tr1::unordered_set;
}
#endif

Let's look at several functions:

#include <bits/stdc++.h>
#if(__cplusplus == 201103L)
#include <unordered_map>
#include <unordered_set>
#else
#include <tr1/unordered_map>
#include <tr1/unordered_set>
namespace std
{
    using std::tr1::unordered_map;
    using std::tr1::unordered_set;
}
#endif
using namespace std;
const int maxn = 1e5 + 100;
unordered_map<int, int> fa;
int main() {
    fa[. 1 ] = 2 ; 
    FA [ 2 ] = . 3 ; 
    FA [ . 3 ] = . 4 ; 
    FA [ . 4 ] = 0 ;
     // COUNT query function key has a value 0 or returns. 1 
    COUT << fa.count ( . 5 ) < <endl; // 0 
    COUT << fa.count ( . 4 ) << endl; // . 1 
    COUT << fa.count ( . 3 ) << endl; // . 1 
    IF (fa.find ( . 1 ) == FA. End ()) << COUT " absent " << endl; // presence of 
    the else COUT <<" Presence " << endl;
     IF (fa.find ( . 4 ) fa.end == ()) << COUT " absent " << endl; // presence of 
    the else COUT << " presence " << endl;  
     IF ( fa.find ( . 5 ) fa.end == ()) << COUT " absent " << endl; // absent 
    the else COUT << " presence " << endl; 
    
    // iterate FA 
    unordered_map < int , int > ::
    iterator it;
    for(IT = fa.begin (); IT =! fa.end ();) 
    { 
        COUT << IT-> First << "  " << IT-> SECOND << endl;
         ++ IT; 
     } 
     COUT << endl << endl;
      // remove a key element of an odd number 
     for (IT = fa.begin ();! IT = fa.end ();) 
    { 
        IF (IT-> First% 2 == . 1 ) IT fa.erase = (IT); // then points to the next delete 
        the else ++ IT; 
     } 
     for (IT = fa.begin (); IT =! fa.end ();) 
    { 
        COUT << IT-> First < < " "<<it->second<<endl;
        ++it;
     } 
    return 0;
}