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Merge K Sorted Lists in Python with heapq

Merge k sorted lists into one sorted list in O(N log k) time using a min-heap of current elements.

import heapq

def merge_k_sorted_lists(lists):
    heap = []
    for i, lst in enumerate(lists):
        if lst:  # only push non-empty lists
            heapq.heappush(heap, (lst[0], i, 0))
    result = []
    while heap:
        val, list_idx, elem_idx = heapq.heappop(heap)
        result.append(val)
        if elem…

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