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Grokking the Coding Interview Patterns

Solution: Kth Smallest Number in M Sorted Lists

Explore the k-way merge technique to find the kth smallest number among multiple sorted lists. Understand how to use a min heap to efficiently merge elements, track positions, and optimize time complexity. This lesson helps you implement and analyze a solution suitable for large data sets, improving your problem-solving skills for coding interviews.

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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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