Flatten and Remove Keys from Dictionary

d = {"a": 1, "b": {"c": 2, "d": {"e": 3, "f": 1}, "g": 1}, "h": [1, {"i": 1, "j": 4}]}
a = 1  
s = [d]  
while s:
    c = s.pop()  
    k = [key for key, val in c.items() if val == a]  

    # Delete the keys that have value 'a'
    for key in k:  
        del c[key]  

    # Check for nested dictionaries or lists in  current dictionary
    for key, val in c.items():
        if isinstance(val, dict):
            s.append(val)  
        
        # If the value is a list, check its items for dictionaries and add them to the stack
        elif isinstance(val, list):
            for item in val:
                if isinstance(item, dict):  
                    # Add dictionaries found in the list to the stack
                    s.append(item)  
print(d)  

from collections import deque

d = {'a': {'b': 1, 'c': {'d': 2}}, 'e': 3}
q = deque([(d, '')])
f = {}

while q:
    c, p = q.popleft() 
    for key, value in c.items():
        new_key = f"{p}.{key}" if p else key
        
        if isinstance(value, dict):
             # Add nested dictionary to the queue
            q.append((value, new_key)) 
            
        else:
            # Add flattened key-value pair
            f[new_key] = value  

print(f)

from itertools import chain
d = {'a': {'b': 1, 'c': {'d': 2}}, 'e': 3}
f = {}
s = [(d, '')]
while s:
    c, p = s.pop()
    
    # Iterate over all key-value pairs in the current dictionary
    for key, value in c.items():
        # Construct the new key by combining parent key and current key
        new_key = f"{p}.{key}" if p else key
        
        #add it back to the stack with the new key
        if isinstance(value, dict):
             s.append((value, new_key))
            
        else:
          
            # If the value is not a dictionary
            f[new_key] = value
print(f)