Search a 2D Matrix II.cpp

/*
Search a 2D Matrix II
=====================

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.

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.
*/

class Solution
{
public:
  bool searchMatrix(vector<vector<int>> &matrix, int target)
  {
    if (!matrix.size() || !matrix[0].size())
      return false;
    int n = matrix.size(), m = matrix[0].size();
    int r = 0, c = m - 1;

    while (r < n && c >= 0)
    {
      if (matrix[r][c] == target)
        return true;
      else if (matrix[r][c] > target)
        c--;
      else
        r++;
    }

    return false;
  }
};