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.

public class Solution {
	public boolean searchMatrix(int[][] matrix, int target) {
		int row = matrix.length;
		int left = 0;
		int right = row - 1;
		int mid = (left + right) / 2;
		while (left <= right) {
			mid = (left + right) / 2;
			if (target == matrix[mid][0]) {
				return true;
			} else if (target < matrix[mid][0]) {
				right = mid-1;
			} else {
				left = mid+1;
			}
		}
		if (target < matrix[mid][0]){
			if(mid == 0){
				return false;
			}else{
				return Arrays.binarySearch(matrix[mid-1], target)>=0;
			}
		}
		return Arrays.binarySearch(matrix[mid], target)>=0;
	}
}

[LeetCode]Search a 2D Matrix