leetcode378

public class Solution {
    public int KthSmallest(int[,] matrix, int k) {
        var row = matrix.GetLength();
            var col = matrix.GetLength();

            var list = new List<int>();

            for (int i = ; i < row; i++)
            {
                for (int j = ; j < col; j++)
                {
                    list.Add(matrix[i, j]);
                }
            }

            list = list.OrderBy(x => x).ToList();
            return list[k - ];
    }
}

https://leetcode.com/problems/kth-smallest-element-in-a-sorted-matrix/#/description

补充一个多次使用二分查找的解决方案：

 public class Solution {
     public int KthSmallest(int[][] matrix, int k) {
         int low = matrix[][];
         int high = matrix[matrix.Length - ][matrix[].Length - ];
         int count = ;
         while (low <= high)
         {
             int mid = low + (high - low) / ;
             count = GetCount(matrix, mid);
             if (count < k)
             {
                 low = mid + ;
             }
             else
             {
                 high = mid - ;
             }
         }
         return low;
     }

     private int GetCount(int[][] matrix, int num)
     {
         int ans = ;
         int i = ;
         int j = matrix[].Length - ;
         while (i < matrix.Length && j >= )
         {
             if (matrix[i][j] > num)
             {
                 j--;
             }
             else
             {
                 ans += j + ;
                 i++;
             }
         }
         return ans;
     }
 }