如何编写程序移除列表中重复项间元素及第二个重复项

How It Works #

We use a while loop to step through the input list, keeping track of elements we've already added to our result with a dictionary (so we can quickly find where an element first appeared):

• When we hit an element we haven't seen before, we add it to the result and note its position.
• If we encounter an element we've already added:
  • Cut the result list off right after the first occurrence of this element (keeping only the first instance, ditching everything after it in the result).
  • Reset our tracking dictionary to match the shortened result.
  • Skip ahead in the input list until we pass the second duplicate (removing it and everything between the two duplicates).
• Repeat until we've processed the entire input list.

Code #

def process_duplicate_pairs(input_list):
    result = []
    seen = {}
    i = 0
    n = len(input_list)
    
    while i < n:
        current_elem = input_list[i]
        
        if current_elem not in seen:
            seen[current_elem] = len(result)
            result.append(current_elem)
            i += 1
        else:
            # Truncate result to retain only up to the first occurrence
            result = result[:seen[current_elem] + 1]
            # Reset tracking dict for the updated result
            seen = {elem: idx for idx, elem in enumerate(result)}
            # Skip past the second duplicate element
            while i < n and input_list[i] != current_elem:
                i += 1
            i += 1  # Move to the next element after the duplicate
    
    return result

Test Examples #

Example 1 #

a = [(0,0),(1,0),(2,0),(3,0),(1,0)]
print(process_duplicate_pairs(a))  # Output: [(0, 0), (1, 0)]

Example 2 #

b = [(0,0),(1,0),(2,0),(3,0),(1,0),(5,0),(6,0),(7,0),(8,0),(5,0),(9,0),(10,0)]
print(process_duplicate_pairs(b))  # Output: [(0, 0), (1, 0), (5, 0), (9, 0), (10, 0)]

Note: The expected result in the problem statement for example 2 omits (10,0), but since this element has no duplicates, it should be retained in the output as per the problem's description.

内容的提问来源于stack exchange，提问作者momo123321