More Maps

#include <iostream>
#include <vector>
#include <unordered_map> //c++11
#include <map>

using namespace std;

int main()

{
    //    key     value
    unordered_map < string, int >  na;
    //map < string, int >  na;
    na["bob"] = 23; // add key/value pairs
    na["sarah"]= 21;
    na["bob"] = 5; //overwrite
    na["bill"] = 8;
    na["adam"]= 200;
    na["zion"]= 3;
    na["cathy"]=55;

    na.erase("sarah");
    //three ways to iterate
    //
    //1
    //map<string,int>::const_iterator i;
    //for (i=na.begin(); i!=na.end(); i++)
    for (auto i=na.begin(); i!=na.end(); i++)
        cout<< i->first << ": " << i->second << endl;
    //        key                 value

    cout<<endl;
    /*
    //if container is a map (not unordered_map)
    //we can iterate backwards
    for (auto i=na.rbegin(); i!=na.rend(); i++)
        cout<< i->first << ": " << i->second << endl;
    */
    cout<<endl;
    na["sarah"]=11;
    //2
    //c++11
    for (auto x: na) //auto &x  and auto const &x
    {
        cout << x.first<< ": "<< x.second << endl;
        if (x.first=="sarah")
            na["sarah"]=22;
    }

    cout<<endl;
/*
    //3
        //c++17
        for (auto [k, v]: na )
            cout << k << ": " << v <<endl;
*/
    //cout<<na["bill"]<<endl; //returns value 0 but also adds bill,0 to map (na["bill]=0)
    //cout<<na.at("bill")<<endl; //fails
    //does key bob exist
    if (na.find("bill") != na.end())
    {
        cout << "found bill  "<<na["bill"] << endl;
    }
    else
    {
        cout<< "bill is not a  key in the map"<<endl;
    }

    //alternate find
    //if we need to store iterator location to access pair
    unordered_map<string, int>::iterator p;
    //map<string, int>::iterator p;
    if ((p=na.find("sarah"))!=na.end())
    {
        cout<< "found "<< p->first <<" "<< p->second <<endl;
    }

    //second alternate find with  easier syntax
    auto q=na.find("sarah");
    if (q != na.end())
    {
        cout<< "found "<< q->first <<" "<< q->second <<endl;
    }


        return 0;
}