Bench 'Hash' for VC++

// cl.exe /EHsc /Ox hash.cpp
#include <iostream>
#include <string>
#include <unordered_map>
#include <stdlib.h>

using namespace std;


int main(int argc, char *argv[])
{
    int n = ((argc == 2) ? atoi(argv[1]) : 1);
    unordered_map<string, int> X;

    char hexString[20];

    for (int i=1; i<=n; i++) {
        itoa(i, hexString, 16);
        X[ strdup(hexString) ] = i;
    }

    int c = 0;
    for (int i=n; i>0; i--) {
        if (X.find(to_string(i)) != X.end()) c++;
    }

    cout << c << endl;
}