HardHeap / Priority Queue

Merge k Sorted Lists

Merge k sorted linked lists

Solution Approach

Divide problem into subproblems, solve each recursively, combine results. Classic examples: merge sort, quick sort, binary tree problems.

Implementation

def mergeSort(arr):
    if len(arr) <= 1:
        return arr
    mid = len(arr) // 2
    left = mergeSort(arr[:mid])
    right = mergeSort(arr[mid:])
    return merge(left, right)

def merge(left, right):
    result = []
    i = j = 0
    while i < len(left) and j < len(right):
        if left[i] <= right[j]:
            result.append(left[i])
            i += 1
        else:
            result.append(right[j])
            j += 1
    return result + left[i:] + right[j:]

Complexity Analysis

Time Complexity

O(n log n)

Space Complexity

O(n)

Key Learning Points

Divide into subproblemsRecursive solutionCombine subresults