std::flat_map::begin,(3)

NAME
std::flat_map::begin, - std::flat_map::begin,

Synopsis
   iterator begin() noexcept; (1) (since C++23)
   const_iterator begin() const noexcept; (2) (since C++23)
   const_iterator cbegin() const noexcept; (3) (since C++23)
   Returns an iterator to the first element of the flat_map.
   If the flat_map is empty, the returned iterator will be equal to end().
   range-begin-end.svg

Parameters
   (none)

Return value
   Iterator to the first element.

Complexity
   Constant.

Example
// Run this code
 #include <iostream>
 #include <flat_map>
 int main()
 {
     std::flat_map<int, double> map{{4, 4.13}, {9, 9.24}, {1, 1.09}};
     for (auto it = map.cbegin(); it != map.cend(); ++it)
         std::cout << '[' << it->first << "] = " << it->second << '\n';
     // Unlike std::map's bidirectional iterators, the std::flat_map iterators
     // are random-access, so they can be used with the operator[]:
     auto it = map.cbegin();
     assert(it[0] == map[1]);
     assert(it[1] == map[4]);
     assert(it[2] == map[9]);
 }

Output:
 [1] = 1.09
 [4] = 4.13
 [9] = 9.24

See also
   end returns an iterator to the end
   cend (public member function)
   begin
   cbegin returns an iterator to the beginning of a container or array
   (C++11) (function template)
   (C++14)