LeetCode:Search a 2D Matrix II

Problem:

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 in ascending from left to right.
• Integers in each column are sorted in ascending from top to bottom.

For example,

Consider the following matrix:

[
  [1,   4,  7, 11, 15],
  [2,   5,  8, 12, 19],
  [3,   6,  9, 16, 22],
  [10, 13, 14, 17, 24],
  [18, 21, 23, 26, 30]
]

Given target = 5, return true.

Given target = 20, return false.

Solution: 

class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
          
        int n=matrix.size();
        int m=matrix[0].size();
        
        
        int row=0;
        int column=m-1;
        
        while(row<n&&column>=0)
        {
            if(matrix[row][column]==target)
                return true;
            else if(matrix[row][column]>target)
                column--;
            else
                row++;
        }
        
        return false;
        
    }
};