How can I modify values in a map using range based for loop?

by

You can turn auto into auto& if you want to mutate/modify the container, for instance:

#include <map>
#include <iostream>

int main()
{
  std::map<int, int> foobar({{1,1}, {2,2}, {3,3}});
  for(auto& p : foobar) {
    ++p.second;
    std::cout << '{' << p.first << ", " << p.second << "} ";
  }
  std::cout << std::endl;
}

compiles ands outputs 

{1, 2} {2, 3} {3, 4}

live example

More Related Contents:

  1. How to use range-based for() loop with std::map?
  2. how to change to c code while using for loop and array
  3. How to solve this for-loop exercise in c++ (beginner). n + nx2 + nx2x2 +
  4. Map C++ Sort and Insert elements by value
  5. Triple Nested For loop (C++) [closed]
  6. How can I use std::maps with user-defined types as key?
  7. How to make my custom type to work with “range-based for loops”?
  8. Why use iterators instead of array indices?
  9. What is the advantage of using forwarding references in range-based for loops?
  10. Post-increment and pre-increment within a ‘for’ loop produce same output [duplicate]
  11. Why can’t I compile an unordered_map with a pair as key?
  12. Can I use break to exit multiple nested ‘for’ loops?
  13. Const map element access
  14. How to find if a given key exists in a C++ std::map
  15. std::map emplace without copying value
  16. Range-for-loops and std::vector
  17. How do I put two increment statements in a C++ ‘for’ loop?
  18. Performance issue for vector::size() in a loop in C++
  19. What is the fastest way to change a key of an element inside std::map
  20. How can I use an array as map value?
  21. Translating python dictionary to C++
  22. converting a variable name to a string in C++
  23. What does `auto && e` do in range-based for-loops?
  24. std::map thread-safety
  25. Creating N nested for-loops
  26. Hashtable in C++?
  27. Are IEEE floats valid key types for std::map and std::set?
  28. map with incomplete value type
  29. C++ “error: passing ‘const std::map’ as ‘this’ argument of …”
  30. C++ inserting unique_ptr in map

Leave a Comment