## Description

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.

Example 1:

``````Input:
matrix = [
[1,   3,  5,  7],
[10, 11, 16, 20],
[23, 30, 34, 50]
]

target = 3
Output: true

target = 13
Output: false
``````

## Solution

 `````` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 `````` ``````func searchMatrix(matrix [][]int, target int) bool { l, r := 0, len(matrix)-1 // 先二分查找在哪一行 for l < r { m := r - (r-l)/2 if target >= matrix[m][0] { l = m } else { r = m - 1 } } // conner case if l > len(matrix)-1 { return false } row := matrix[l] l, r = 0, len(row)-1 // 再在对应行中进行二分查找 for l <= r { m := l + (r-l)/2 if target == row[m] { return true } if target > row[m] { l = m + 1 } else { r = m - 1 } } return false }``````