kth_smallest_element_in_a_sorted_matrix.py

#!/usr/bin/python
# -*- coding: utf-8 -*-
"""
Given a n x n matrix where each of the rows and columns are sorted in ascending order, find the kth smallest element in the matrix.

Note that it is the kth smallest element in the sorted order, not the kth distinct element.

Example:

matrix = [
   [ 1,  5,  9],
   [10, 11, 13],
   [12, 13, 15]
],
k = 8,

return 13.
"""


class Solution(object):
    def kthSmallest(self, matrix, k):
        """
        :type matrix: List[List[int]]
        :type k: int
        :rtype: int
        """
        return self.ans(matrix, k)

    def ans(self, matrix, k):
        if len(matrix) == 0 or len(matrix[0]) == 0 or k <= 0:
            return None

        from Queue import PriorityQueue

        pq = PriorityQueue()

        for i in range(len(matrix)):
            for j in range(len(matrix[0])):
                pq.put((matrix[i][j], matrix[i][j]))

        i = 0
        res = None
        while i < k:
            if not pq.empty():
                res = pq.get()[1]
            i += 1

        return res


if __name__ == "__main__":
    matrix = [[1, 5, 9],
              [10, 11, 13],
              [12, 13, 15]]
    k = 8

    print(Solution().kthSmallest(matrix, k))