unordered_map.cpp

// C++ program to demonstrate functionality of unordered_map 
#include <iostream> 
#include <unordered_map> 
using namespace std; 

int main() 
{ 
	// Declaring umap to be of <string, double> type 
	// key will be of string type and mapped value will 
	// be of double type 
	unordered_map<string, double> umap; 

	// inserting values by using [] operator 
	umap["PI"] = 3.14; 
	umap["root2"] = 1.414; 
	umap["root3"] = 1.732; 
	umap["log10"] = 2.302; 
	umap["loge"] = 1.0; 

	// inserting value by insert function 
	umap.insert(make_pair("e", 2.718)); 

	string key = "PI"; 

	// If key not found in map iterator to end is returned 
	if (umap.find(key) == umap.end()) 
		cout << key << " not found\n\n"; 

	// If key found then iterator to that key is returned 
	else
		cout << "Found " << key << "\n\n"; 

	key = "lambda"; 
	if (umap.find(key) == umap.end()) 
		cout << key << " not found\n"; 
	else
		cout << "Found " << key << endl; 

	// iterating over all value of umap 
	unordered_map<string, double>:: iterator itr; 
	cout << "\nAll Elements : \n"; 
	for (itr = umap.begin(); itr != umap.end(); itr++) 
	{ 
		// itr works as a pointer to pair<string, double> 
		// type itr->first stores the key part and 
		// itr->second stroes the value part 
		cout << itr->first << " " << itr->second << endl; 
	} 
}