(C++ STL) Benchmarking Find for Vector and Unordered Set

bench.cpp

#include <vector>
#include <set>
#include <unordered_set>
#include <cassert>
#include <iostream>
#include <ctime>
#include <unistd.h>
#include <chrono>
#include <algorithm>
#include <vector>

#define LEN 23

using namespace std;
using std::chrono::high_resolution_clock;
using std::chrono::duration_cast;
using std::chrono::duration;
using std::chrono::milliseconds;

int random_number(int min, int max)
{
   static bool first = true;
   if (first) 
   {  
      srand( time(NULL) );
      first = false;
   }
   return min + rand() % (( max + 1 ) - min);
}

string random_string(const int len)
{
    string tmp_s;
    static const char alphanum[] =
        "0123456789"
        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        "abcdefghijklmnopqrstuvwxyz";
    
    srand( (unsigned) time(NULL) * getpid());

    tmp_s.reserve(len);

    for (int i = 0; i < len; ++i) 
        tmp_s += alphanum[rand() % (sizeof(alphanum) - 1)];
    
    return tmp_s;
}

void test_vec(long long int size)
{
    // cout << "Testing vec..." << endl;

    vector<string> vec;
    int index = random_number(0, size-1);
    string find;

    for(int i = 0; i<size; ++i)
    {
        string temp = random_string(LEN);
        vec.push_back(temp);
        if(i==index)
            find = temp;
    }
    auto t1 = high_resolution_clock::now();
    if(std::find(vec.begin(), vec.end(), find) == vec.end())
        cout << "Failed!" << endl;
    auto t2 = high_resolution_clock::now();

    duration<double, std::milli> ms_double = t2 - t1;
    cout << ms_double.count() << endl;

}

void test_set(long long int size)
{
    // cout << "Testing set..." << endl;

    unordered_set<string> set;
    int index = random_number(0, size-1);
    string find;

    for(int i = 0; i<size; ++i)
    {
        string temp = random_string(LEN);
        set.insert(temp);
        if(i==index)
            find = temp;
    }

    auto t1 = high_resolution_clock::now();
    if(set.find(find) == set.end())
        cout << "Failed!" << endl;
    auto t2 = high_resolution_clock::now();

    duration<double, std::milli> ms_double = t2 - t1;
    cout << ms_double.count() << endl;
    
}

int main()
{
    for(long long int size = 100; size<=100000000; size*=10)
    {
        cout << size << endl;
        test_vec(size);
        test_set(size);
    }
    
    return 0;
}