How Do I Iterate Through a Nested Map in C ?

Looping through a Nested C Map of Maps

To iterate over a nested map in C , where the map contains a map of strings to strings, you can utilize the ranged-based for loop syntax. Here's an updated solution for C 11 and beyond:

std::map<std::string, std::map<std::string, std::string>> mymap;

for (const auto &[outer_key, inner_map] : mymap) {
  // Outer key is accessible via 'outer_key'
  for (const auto &[inner_key, inner_value] : inner_map) {
    // Inner key is accessible via 'inner_key'
    // Inner value is accessible via 'inner_value'
  }
}

This approach eliminates unnecessary copies and provides a concise and elegant way to access the keys and values in the nested map.

For C 17, you can simplify this even further using structured bindings:

for (const auto &[outer_key, inner_map] : mymap) {
  for (const auto &[inner_key, inner_value] : inner_map) {
    // Access your 'outer_key', 'inner_key', and 'inner_value' directly
  }
}

This technique allows you to directly access the variables without having to define intermediate references like ent1, ent2, and so on.

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