I have written a Python function called merge_arrays which takes an tow list and returns the new list merge without duplicate. The function works as expected, but my code very complicated, and I'm looking for ways to optimize it. Below is my current implementation:

def update_if_new(d, results, element):
 if element not in d:
 results.append(element)
 d[element] = True
 
def merge_arrays(first, second): 
 seen = dict()
 results = []
 i, j, m, n = 0, 0, len(first), len(second)
 
 while i < m and j < n:
 x, y = first[i], second[j]
 if x < y:
 update_if_new(seen, results, x)
 i += 1
 else:
 update_if_new(seen, results, y)
 j += 1
 
 for residual in first[i:] + second[j:]:
 update_if_new(seen, results, residual)
 
 return results
print(merge_arrays([1,2,3],[5,7,1]))
#[1, 2, 3, 5, 7]

I'm seeking suggestions for improvements in the code to make it more efficient and reduce the execution time. Any tips or alternative solutions would be greatly appreciated.

I have written a Python function called merge_arrays which takes two lists and returns the new list merge without duplicate.
The function works as expected, but my code very complicated, and I'm looking for ways to optimize it.
Below is my current implementation:

def update_if_new(d, results, element):
 if element not in d:
 results.append(element)
 d[element] = True
 
def merge_arrays(first, second): 
 seen = dict()
 results = []
 i, j, m, n = 0, 0, len(first), len(second)
 
 while i < m and j < n:
 x, y = first[i], second[j]
 if x < y:
 update_if_new(seen, results, x)
 i += 1
 else:
 update_if_new(seen, results, y)
 j += 1
 
 for residual in first[i:] + second[j:]:
 update_if_new(seen, results, residual)
 
 return results
print(merge_arrays([1,2,3],[5,7,1]))
#[1, 2, 3, 5, 7]

I'm seeking suggestions for improvements in the code to make it more efficient and reduce the execution time.
Any tips or alternative solutions would be greatly appreciated.