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Solution: Kth Smallest Number in M Sorted Lists

Explore efficient methods to find the kth smallest number in multiple sorted lists. Understand the naive and optimized k-way merge algorithms, focusing on time and space complexity. Learn to implement a min heap to merge sorted lists and track elements, enabling you to solve this common coding interview problem effectively.

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Statement

Given a list, lists, containing mm sorted lists of integers in ascending order, and an integer k, find the kthk^{th} smallest element among all the lists.

Even if some values appear multiple times across the lists, each occurrence is treated as a unique element when determining the kthk^{th} smallest number.

If k exceeds the total number of elements across all lists, return the largest element among them. If the lists are empty, return 0.

Constraints:

  • 1≤m≤501\leq m \leq50
  • 0≤0\leq lists[i].length ≤50\leq 50
  • −109≤-10^9\leq lists[i][j] ≤109\leq 10^9
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