LeetCode Online Judge 题目C# 练习 - Search a 2D Matrix

Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:
Integers in each row are sorted from left to right.
The first integer of each row is greater than the last integer of the previous row.
For example,
Consider the following matrix:

[
 [1, 3, 5, 7],
 [10, 11, 16, 20],
 [23, 30, 34, 50]
]
Given target = 3, return true.

 1         public static bool Searcha2DMatrix(List<List<int>> matrix, int target)

 2         {

 3             int i = 0, j = 0;

 4 

 5             while (i < matrix.Count && j < matrix[i].Count)

 6             {

 7                 if (matrix[i][j] == target)

 8                     return true;

 9                 if (i + 1 < matrix.Count && matrix[i + 1][j] <= target)

10                     i++;

11                 else if (j + 1 < matrix[i].Count && matrix[i][j + 1] <= target)

12                     j++;

13                 else

14                     return false;

15             }

16 

17             return false;

18         }

代码分析：

　　先往下，不能往下就往右。