LeetCode--Search a 2D Matrix

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.

For example,

Consider the following matrix:

[
  [1,   3,  5,  7],
  [10, 11, 16, 20],
  [23, 30, 34, 50]
]

Given target = 3, return true.

#include<vector>
using std::vector;
class Solution 
{
public:
	bool searchMatrix(vector<vector<int> > &matrix, int target) 
	{
		int n = matrix.size();
		if(n==0)
			return false;
		int m = matrix[0].size();
		int low = 0;
		int high = n-1;
		while(low <= high)
		{
			int mid = (low+high)/2;
			if(matrix[mid][0] == target)
				return true;
			else if(matrix[mid][0] > target)
				high = mid-1;
			else
				low = mid+1;
		}
		if(high < 0)
			return false;
		int loc = high;
		low = 0;
		high = m-1;
		while(low <= high)
		{
			int mid = (low+high)/2;
			if(matrix[loc][mid] == target)
				return true;
			else if(matrix[loc][mid] > target)
				high = mid-1;
			else
				low = mid+1;
		}
		return false;
	}
};