lintcode-medium-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.

 

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] == null || matrix[0].length == 0)
            return 0;
        
        int m = matrix.length;
        int n = matrix[0].length;
        
        int x = 0;
        int y = m - 1;
        
        int count = 0;
        
        while(x < n && y >= 0){
            if(matrix[y][x] > target){
                y--;
            }
            else if(matrix[y][x] < target){
                x++;
            }
            else{
                count++;
                x++;
                y--;
            }
        }
        
        return count;
    }
}

 

posted @ 2016-04-05 16:51  哥布林工程师  阅读(130)  评论(0编辑  收藏  举报