Introduction

Hello, and welcome back to our coding lesson series. In this unit, we have a fascinating problem at hand that uses the concept of 2D arrays or grids. What's interesting about this problem is that it involves not only the simple traversal of the grid but also performing this traversal in a unique manner. Initially, the concept might seem a bit tricky, but as we dissect the task and take it step by step, you're sure to enjoy how it unfolds. Are you ready to embark on this adventure? Let's dive right in!

Task Statement

The task before us involves the creation of a Ruby method named path_traverse. This method should perform a particularly ordered traversal through a 2D grid. The method will accept a grid, along with the starting cell coordinates, as parameters. Starting from the provided cell, the method should make moves in any one of the four possible directions toward an adjacent cell. However, a condition governs this selection: the new cell value should be strictly greater than the current cell's value.

This pattern would continue as we keep selecting the next available larger cell value. The traversal will halt when there are no cells left that satisfy our criteria. The final result of the method will be an array that includes all the visited cell values in the order of their visitation.

Consider a 3x3 grid:

If we start at the cell with the value 5, we can logically move to either 6 or 8. Let's say we choose 6; the only cell we can now move to is 9. After this, we have no more moves left that fit our criteria. Hence, the method returns [5, 6, 9].

Solution Building: Step 1

The first thing we need to do is determine the dimensions of our grid, which is relatively easy in Ruby with properties like size. We can also establish the directions that our traversal can take. In the context of matrices, when we say we are moving "up," we are moving one step towards the first row (decreasing the row index). Similarly, moving "down" corresponds to moving one step towards the last row (increasing the row index), and moving left or right relates to decrementing or incrementing the column index, respectively.

In the directions array, each sub-array represents a direction in terms of a pair [row_offset, col_offset]. So, if we are at a cell (r, c), moving up corresponds to going to the cell (r-1, c), moving down corresponds to (r+1, c), moving left corresponds to (r, c-1), and moving right corresponds to (r, c+1).

Solution Building: Step 2

Once we have the grid's dimensions and the possible directions, we should validate the starting point and set up our visited cell recording mechanism.

Solution Building: Step 3

Let's initiate the grid traversal process in our method. We first set up an infinite loop that will only stop when we break it based on a condition.

Solution Building: Step 4

Inside the infinite loop, for each iteration, we'll have the method try to select the next cell with the maximum value among the adjacent cells. If we find such a cell, we'll capture its value, and it will be our next cell.

Solution Building: Step 5

Finally, if there are no valid neighboring cells to visit, we'll break our infinite loop and return the list of visited cells' values.

In the end, our beautiful method looks like this:

Lesson Summary

Bravo! You've successfully solved a complex problem involving the traversal of a grid in a unique pattern. This method has tested not only your skills in Ruby programming but also your ability to visualize spatial patterns.

Having digested this knowledge, it's now time to test your understanding and apply these concepts to similar problems. Watch out for the ensuing practice session, where you can dabble with more challenging problems and refine your problem-solving skills. Keep up the good work, and happy coding!

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