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) {

        int rows = matrix.size();

        if (rows == 0) {

            return false;

        }

        int cols = matrix[0].size();

        int rows_st = 0;

        int cols_end = cols;

        while (rows_st < rows && cols_end > 0) {

            int row = rows_st, col = cols_end - 1;

            if (matrix[row][col] == target) {

                return true;

            } else if (matrix[row][col] > target) {

                cols_end--;

            } else {

                rows_st++;

            }

        }

        return false;

    }

};