header file for unordered_map in c++
#include<unordered_map> //is the stl for unordered mapheader file for unordered_map in c++
#include<unordered_map> //is the stl for unordered mapunordered_map c++
#include <bits/stdc++.h>
#include <iostream>
#include <map>
#include <unordered_map>
using namespace std;
int main() {
map<char, int> M; //based on balanced binary tree takes O(logn) access time
unordered_map<char, int> U; //uses hashing and accessing elements takes O(1)
//U.add(key,value);
//U.erase(key,value);
//map each letter to their occurance
string s = "Sumant Tirkey";
for (char c : s) {
M[c]++;
}
for (char c : s){
U[c]++;
}
return 0;
}unordered map in c++
#include <unordered_map>
#include <iostream>
int main()
{
std::unordered_map<std::string, int> age;
// Insert
age["Michael"] = 16;
age.insert(std::pair<std::string, int>{"Bill", 25});
age.insert({"Chris", 30});
// Search and change
age["Michael"] = 18;
age.at("Chris") = 27;
// Check if key exists
std::string query;
query = "Eric";
if (age.find(query) == age.end())
{
std::cout << query << " is not in the dictionary!" << std::endl;
}
// Delete
query = "Michael";
if (age.find(query) == age.end())
{
std::cout << query << " is not in the dictionary!" << std::endl;
}
age.erase(query);
if (age.find(query) == age.end())
{
std::cout << query << " is not in the dictionary!" << std::endl;
}
// Iterate
for (const std::pair<std::string, int>& tup : age)
{
std::cout << "Name: " << tup.first << std::endl;
std::cout << "Age: " << tup.second << std::endl;
}
}Copyright © 2021 Codeinu
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