What happens if I read a map's value where the key does not exist?

Question

map dada;
dada[\"dummy\"] = \"papy\";
cout << dada[\"pootoo\"];

I\'m puzzled because I don\'t know if it\'s considered

Answer 1

If you try to access a key value using index operator [], then 2 things can happen :

1. The map contains this key. So it will return the corresponding key value.
2. The map doesn't contain the key. In this case, it will automatically add a key to the map with null value.

"pootoo" key does't exist in your map. So it will automatically add this key with value = ""(empty string). And your program will print empty string.

Here map size will increase by 1.

To search a key you can use map_name.find(), which will return map_name.end() if the key doesn't exist. And no extra key will be added.

You can use [] operator when you want to set value for a key.