Write an efficient algorithm that searches for a value in anmxnmatrix. 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]
]

Giventarget=3, returntrue.

tag: binary search

class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {

        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) return false;

        int n = matrix.length, m = matrix[0].length;


        for (int i = 0; i < n; i++){
            if (matrix[i][m - 1] < target) continue;

            int left = 0, right = m - 1;
            while (left + 1 < right){
                int mid = left + (right- left) / 2;
                if (matrix[i][mid] == target){
                    return true;
                }
                else if (matrix[i][mid] < target){
                    left = mid;
                }
                else{
                    right = mid;
                }
            }

            if (matrix[i][right] == target) return true;
            if (matrix[i][left] == target) return true;
        }

        return false;
    }
}