Default values in a Map in C++ STL
Prerequisite: Map in STL
A map is a container which is used to store a key-value pair. By default, In Primitive datatypes such as int, char, bool, float in C/C++ are undefined if variables are not initialized, But in a Map, every key is mapped with default value zero when the map is declared. To initialize the map with a random default value below is the approach:
Approach:
- Declare a structure(say struct node) with a default value.
- Intialise Map with key mapped to struct node.
Syntax:
// For Structure
struct Node {
int value = -1;
}
// For Map with every key mapped to default value -1
Map < int, Node > M;
Below is the illustration of the Map with a default value -1:
// C++ program to illustrate a Map // initialise with default value #include <bits/stdc++.h> using namespace std; // Structure Node struct Node { int value = -1; }; // Driver Code int main() { // Map initialise with key value // pair with each pair mapped with // structure Node map<int, Node> Map; // Print the default value of 1 // store in Map cout << Map[1].value << endl; return 0; } |
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Output:
-1
