Fix inputs and add methods

tests/array_vs_hash.cc

@@ -0,0 +1,90 @@
+#include <algorithm>
+#include <chrono>
+#include <iostream>
+#include <random>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+using namespace std;
+using namespace std::chrono;
+
+int N = 1000000; // 1,000,000 tries
+int L = 20;      // string length
+
+string random_string(size_t length) {
+  static const string chars =
+    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+
+  static random_device rd;
+  static mt19937 gen(rd());
+
+  uniform_int_distribution<> dist(0, chars.size() - 1);
+
+  string s;
+
+  for (size_t i = 0; i < length; i++) {
+    s += chars[dist(gen)];
+  }
+
+  return s;
+}
+
+void test_array(int length) {
+  std::unordered_map<std::string, int> hash_map;
+  hash_map.reserve(length * 2); // Reserve more to avoid rehashing
+  std::vector<std::pair<std::string, int>> array;
+  array.reserve(length);
+
+  vector<string> keys;
+
+  for (int i = 0; i < length; ++i) {
+    string key = random_string(L);
+
+    keys.push_back(key);
+
+    hash_map[key] = i;
+    array.emplace_back(key, i);
+  }
+
+  auto start = std::chrono::high_resolution_clock::now();
+  for (int i = 0; i < N; ++i) {
+    string &key = keys[i % length];
+
+    auto it = hash_map.find(key);
+
+    volatile int value = it->second;
+    (void)value;
+  }
+  auto end = std::chrono::high_resolution_clock::now();
+  auto hash_duration = std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count();
+
+  start = std::chrono::high_resolution_clock::now();
+  for (int i = 0; i < N; ++i) {
+    string &key = keys[i % length];
+
+    auto it = std::find_if(array.begin(), array.end(), [&key](const auto &pair) {
+      return pair.first == key;
+    });
+
+    volatile int value = it->second;
+    (void)value;
+  }
+  end = std::chrono::high_resolution_clock::now();
+  auto array_duration = std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count();
+
+  std::cout << length << "," << hash_duration << "," << array_duration << "\n";
+}
+
+int main() {
+  std::cout << "elements,hash,array\n";
+
+  for (int length = 1; length <= 10; length++)
+    test_array(length);
+  for (int length = 10; length <= 100; length += 10)
+    test_array(length);
+  for (int length = 100; length <= 1000; length += 100)
+    test_array(length);
+
+  return 0;
+}