UnorderedMap.cpp

#include <iostream>
#include <unordered_map>
using namespace std;

struct Info
{
    string name;
    uint32_t score;
};

int main()
{
    // Add to a map and print it out
    {
        unordered_map<char, Info> myMap;
        myMap['a'] = {"apple", 5};
        myMap['b'] = {"boy", 8};
        myMap['c'] = {"cat", 7};

        for (auto itr = myMap.begin(); itr != myMap.end(); itr++)
        {
            cout << itr->first << ": " << itr->second.name << " , " << itr->second.score << endl;
        }
        cout << endl;

        for (auto itr = myMap.begin(); itr != myMap.end(); itr++)
        {
            itr->second.score = 5;
        }

        for (auto itr = myMap.begin(); itr != myMap.end(); itr++)
        {
            cout << itr->first << ": " << itr->second.name << " , " << itr->second.score << endl;
        }
        cout << endl;
    }

    // Add unique elements to a map and print it out
    {
        unordered_map<int, int> sampIntHash;

        //int a[7] = {5, 6, 7, 8, 6, 9, 7};
        char a[7] = {'v', 'q', 'b', 'l', 'q', 'c', 'b'};

        for (unsigned int i = 0; i < sizeof(a)/sizeof(char); i++)
        {
            cout << "A: " << a[i] << " " << endl;

            auto tmpIntHash = sampIntHash.find(a[i]);

            if (tmpIntHash != sampIntHash.end())
            {
                cout << "Present" << endl;
            }
            else
            {
                sampIntHash[a[i]] = i;
            }
        }

        for (auto itr = sampIntHash.begin(); itr != sampIntHash.end(); itr++)
        {
            cout << "Itr: " << itr->first << " : " << itr->second << endl;
        }
    }

    // Efficient way to count unique characters in a string
    {
        string str = "hello world";
        unordered_map<char, uint32_t> uniqCharsMap1;
        unordered_map<char, uint32_t> uniqCharsMap2;
        
        // Not a nice way
        for (char c : str)
        {
            auto itr = uniqCharsMap1.find(c);

            if (itr != uniqCharsMap1.end())
            {
                itr->second++;
            }
            else
            {
                uniqCharsMap1[c] = 1;
            }
        }

        // A better way to get the same
        for (char c : str)
        {
            ++uniqCharsMap2[c];
        }

        cout << endl << "Map 1" << endl;
        for (auto itr = uniqCharsMap1.begin(); itr != uniqCharsMap1.end(); itr++)
        {
            cout << "Itr: " << itr->first << " : " << itr->second << endl;
        }
        cout << endl << "Map 2" << endl;

        for (auto itr = uniqCharsMap2.begin(); itr != uniqCharsMap2.end(); itr++)
        {
            cout << "Itr: " << itr->first << " : " << itr->second << endl;
        }

    }

    return 0;
}