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.
- Initialize 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:
CPP14
// C++ program to illustrate a Map// initialize with default value#include <bits/stdc++.h>using namespace std; // Structure Nodestruct Node { int value = -1;}; // Driver Codeint main(){ // Map initialize 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;} |
Output:
-1
