LeetCode 378. Kth Smallest Element in a Sorted Matrix

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.

Note:

You may assume k is always valid, 1 ≤ k ≤ n2.

C# AC 代码：

public class Solution
{
public int FindKSmallest(int[,] matrix, int k)
{
int count = 0;
int mid = 0;
int n = matrix.GetLength(0);
int l = matrix[0, 0] ,r = matrix[n-1, n-1];
while (l <= r)
{
mid = l + (r - l) / 2;
count = GetNmumberLessThanV(matrix, mid);
if (count < k)
{
l = mid + 1;
}
else
{
r = mid - 1;
}
}
return l;
}

public int GetNmumberLessThanV(int[,]a, int v)
{
int count = 0;
int i = a.GetLength(0)- 1, j = 0;
/*从左下角开始比较，因为左下角所在列都比当前值小，只要这个值小所在列都包括,此时列数加1，如果不是，则
*行数-1，直接排除一行
*依次类推
*/
while(i >= 0 && j< a.GetLength(1))
{
if(a[i,j]>v)
{
i--;
}
else
{
j++;
count += i+1;
}
}
return count;
}
}

python AC

这个其实相当去全排列 ，没办法谁让python这么强大 代码贼短

class Solution(object):
def kthSmallest(self, matrix, k):
"""
:type matrix: List[List[int]]
:type k: int
:rtype: int
"""
b = []
for l in matrix:
b.extend(l)
b.sort()
return b[k-1]