Merge Nested Dictionaries Iteratively

Given a list of Python dictionaries, merge them into a single dictionary **without using recursion**. Rules: - Process the dictionaries from left to right. - If a key appears in only one dictionary, keep that key-value pair. - If the same key appears in multiple dictionaries: - when both values are dictionaries, merge those dictionaries using the same rules; - otherwise, the value from the later dictionary overrides the earlier one. - You may assume keys are strings. Example: - Input: - `[{"a": 1, "b": {"x": 2}}, {"b": {"y": 3}, "c": 4}, {"b": {"x": 5}}]` - Output: - `{"a": 1, "b": {"x": 5, "y": 3}, "c": 4}` Implement a function that returns the merged dictionary using an iterative approach.