Create main.cpp

Author: JawadSher

20 - Hashmap Data Structure Problems/01 - Example/main.cpp

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+#include <iostream>
+#include <map>
+#include <unordered_map>
+using namespace std;
+
+int main() {
+  
+  // creation of Unordered Map
+  unordered_map<string, int> um;
+
+  // insertion
+    // Approach 1
+    pair<string, int> p = make_pair("Hello", 1);
+    um.insert(p);
+
+    // Approach 2
+    pair<string, int> p2("World", 2);
+    um.insert(p2);
+
+    // Approach 3
+    pair<string, int> p3{"NewWorld", 3};
+    um.insert(p3);
+
+    // Approach 4
+    um["World"] = 4;
+
+  
+  cout << "-------- Searching --------" << endl;
+  // Searching
+    // Approach 1
+    cout << "Value of 'World' Key : "<< um["World"] << endl;
+
+    // Approach 2
+    cout << "Value of 'World' Key : " <<um.at("NewWorld") << endl;
+
+    // Search for Un-known key
+    // cout << um.at("unknown") << endl; // output : error
+    // cout << um["unknown"] << endl; // output : 0
+
+    // But now change the order at see what it returns.
+    cout << "Value of 'unknown' Key : " << um["unknown"] << endl; // output : 0
+    cout << "Value of 'unknown' Key : " << um.at("unknown") << endl; // output : 0
+
+  // Updation
+    um["World"] = 5;
+
+  cout << "-------- Checking Size --------" << endl;
+  // Size
+  cout << "Size of unordered_map : " << um.size() << endl;
+
+  cout << "-------- Check Presence --------" << endl;
+  // Check Presence
+  cout << "Is 'World' Key Value Present or Not : "<< um.count("World") << endl; // true
+  cout << "Is 'Unknown' Key Value Present or Not : "<< um.count("Unknown") << endl; // false
+
+  // Erase
+  um.erase("World");
+  cout << "Size of unordered_map : " << um.size() << endl;
+
+  cout << "-------- For Loop Iteration --------" << endl;
+  // Iteration
+  for(auto i : um) cout << "Iterting Key Value Pair : " << i.first << " " << i.second << endl;
+
+  cout << "-------- Iterators --------" << endl;
+  // Iterators
+  unordered_map<string, int> :: iterator it = um.begin();
+
+  while(it != um.end()){
+    cout << "Iterting Key Value Pair : " << it->first << " " << it->second << endl;
+    it++;
+  }
+  return 0;
+}