[LintCode] 38 Search a 2D Matrix II

Description
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.


Example
Consider the following matrix:

[
  [1, 3, 5, 7],
  [2, 4, 7, 8],
  [3, 5, 9, 10]
]
Given target = 3, return 2.

4/27/2017

算法班

第17，18行的条件是同一行同一列当中没有重复的元素。

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 col = matrix[0].length - 1, row = 0;
        int count = 0;
        while  (col >= 0 && row < matrix.length) {
            if (matrix[row][col] == target) {
                count++;
                col--;
                row++;
            } else if (matrix[row][col] < target) {
                row++;
            } else {
                col--;
            }
        }
        return count;
    }
}