Search a 2D Matrix II

Write an efficient algorithm that searches for a value in an m x n matrix, return the occurrence of it.

This matrix has the following properties:

    * Integers in each row are sorted from left to right.

    * Integers in each column are sorted from up to bottom.

    * No duplicate integers in each row or column.

Have you met this question in a real interview? 

Yes

Example

Consider the following matrix:

[

    [1, 3, 5, 7],

    [2, 4, 7, 8],

    [3, 5, 9, 10]

]

Given target = 3, return 2.

Challenge

O(m+n) time and O(1) extra space

public class Solution {

    /**

     * @param matrix: A list of lists of integers

     * @param: A number you want to search in the matrix

     * @return: An integer indicate the occurrence of target in the given matrix

     */

    public int searchMatrix(int[][] matrix, int target) {

        // write your code here

        if(matrix == null || matrix.length == 0 || matrix[0].length == 0){

            return 0;

        }

        

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

        int count = 0;

        int i = 0, j = n - 1;

        while(i < m && j >= 0){

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

                count++;

                i++;

                j--;

            } else if(matrix[i][j] > target){

                j--;

            } else {

                i++;

            }

        }

        return count;

    }

}