Leetcode --- Search a 2D Matrix(Medium)
===

## Description

Write an **efficient** algorithm that searches for a value in an m x n matrix. 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.

### Example


**Input**: matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 3
**Output:** ==true==

## Solution
因為每一列都已經被sorted,所以對2D matrix的每一列分別做binary search.

### implement code

import java.util.*;
class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        for(int i =0 ;i<matrix.length;i++)
            if(Arrays.binarySearch(matrix[i],target) >=0)
                return true;
        return false;
    }
}

### Time complexity
Matrix size : nxm
binary search :O(log~m~) m為行數(一列的size)
要做n次 =>
==O(nlog~m~)==

### Submission on Leetcode

Runtime: **0 ms**, faster than **100.00%** of Java online submissions for Search a 2D Matrix.
Memory Usage: **38.3 MB, less than 63.41%** of Java online submissions for Search a 2D Matrix.

###### tags: `Leetcode` `Medium` `Search`