c++ map values range
To map values within a range in C++, you can use a combination of the std::map
container and iterator-based algorithms. Here are the steps involved:
Include the necessary header files: To use the
std::map
container, you need to include the<map>
header file in your code.Create a
std::map
object: Declare and instantiate astd::map
object that will store your key-value pairs. The keys in the map should be unique and ordered.Insert values into the map: Use the
insert()
function or the square bracket[]
operator to insert key-value pairs into the map. The keys will determine the ordering of the values.Find the range: Determine the range of values you want to map. This can be done using the
lower_bound()
andupper_bound()
member functions of thestd::map
container. Thelower_bound()
function returns an iterator pointing to the first element that is not less than a given key, while theupper_bound()
function returns an iterator pointing to the first element greater than a given key.Iterate over the range: Use a loop to iterate over the range of values you obtained from the previous step. You can use the
begin()
andend()
member functions of thestd::map
container to get iterators representing the beginning and end of the map.Perform operations on the mapped values: Within the loop, you can access and perform operations on the mapped values using the iterator. You can use the
->
operator to access the value associated with the iterator.
Here is an example that demonstrates these steps:
#include <iostream>
#include <map>
int main() {
std::map<int, std::string> myMap;
myMap.insert({1, "One"});
myMap.insert({2, "Two"});
myMap.insert({3, "Three"});
myMap.insert({4, "Four"});
myMap.insert({5, "Five"});
auto lower = myMap.lower_bound(2);
auto upper = myMap.upper_bound(4);
for (auto it = lower; it != upper; ++it) {
std::cout << it->second << std::endl;
}
return 0;
}
In this example, we create a std::map
called myMap
and insert five key-value pairs into it. We then use lower_bound(2)
to get an iterator pointing to the element with the key 2, and upper_bound(4)
to get an iterator pointing to the element with the key 4. Finally, we iterate over the range from lower
to upper
and print the corresponding values.
The output of this code will be:
Two
Three
Four
This demonstrates how you can map values within a specific range using a std::map
in C++.