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, return2.

1.this problem can be solved with two binary search like the first problem Search a 2D Matrix

1. there is simpler way, that we start traversing from bottom left or top right, so everytime we compare we remove a entire row or column. (no duplicates in the same row)

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
        int sum = 0;
        if (matrix == null || matrix.length == 0 || matrix[0] == null || matrix[0].length == 0) {
            return sum;
        }

        int startRow = matrix.length - 1;
        int startCol = 0;

        while (startRow >= 0 && startCol < matrix[0].length) {
            if (matrix[startRow][startCol] == target) {
                sum++;
                startRow--;
            } else if (matrix[startRow][startCol] < target) {
                startCol++;
            } else {
                startRow--;
            }
        }

        return sum;

    }
}