How to Safely Remove a Range of Elements from a Map Based on a Condition?

Erasing a Range of Elements from a Map with a Specific Condition

In situations where it's necessary to remove a specific range of elements from a map based on a particular condition, a "remove_if" equivalent algorithm is sought. However, STL's remove_if cannot be applied directly to associative containers like maps.

To achieve this functionality, an alternative approach is to iterate through the map while applying the condition. If the condition is met, the corresponding element is erased. However, erasing elements from within a loop can invalidate iterators.

The following modified loop addresses this issue:

for(; iter != endIter; ) {
  if (predicate(*iter)) {
    iter = aMap.erase(iter);
  } else {
    ++iter;
  }
}

By incrementing the iterator only when the element is not erased, the loop correctly handles the invalidation of iterators. This approach ensures that the desired range of elements is removed, and it is safe to use when iterating through a map.

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