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Kth element in Matrix
Medium Accuracy: 49.98% Submissions: 25831 Points: 4

Given a N x N matrix, where every row and column is sorted in non-decreasing order. Find the kth smallest element in the matrix.

Example 1:
Input:
N = 4
mat[][] =     {{16, 28, 60, 64},
{22, 41, 63, 91},
{27, 50, 87, 93},
{36, 78, 87, 94 }}
K = 3
Output: 27
Explanation: 27 is the 3rd smallest element.

Example 2:
Input:
N = 4
mat[][] =     {{10, 20, 30, 40}
{15, 25, 35, 45}
{24, 29, 37, 48}
{32, 33, 39, 50}}
K = 7
Output: 30
Explanation: 30 is the 7th smallest element.

You don't need to read input or print anything. Complete the function kthsmallest() which takes the mat, N and K as input parameters and returns the kth smallest element in the matrix.

Expected Time Complexity: O(K*Log(N))
Expected Auxiliary Space: O(N)

Constraints:
1 <= N <= 50
1 <= mat[][] <= 10000

1 <= K <= N*N

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