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Class 6 Grids and Movement: cheat sheet
CBSE Computational Thinking and AI. Robots on a grid follow commands like F, L and R. We track the cell and the facing, find the fewest moves and count shortest routes.
Key ideas
- Cells are named (column, row), with (1, 1) at the bottom left; the column is always written first.
- F moves one cell forward in the direction the robot faces; L and R turn it 90° and it stays in the same cell.
- Facing North the row goes up; East, the column goes up; South, the row goes down; West, the column goes down.
- With no walls, the fewest moves between two cells is the steps across plus the steps up or down.
- In a maze, count outwards from the start one ring of squares at a time until you reach the goal.
- For routes moving only right or up, each corner’s count is the corner to its left plus the corner below.
Remember
| Turning right from North | North → East → South → West → North |
| Four right turns | back to the starting direction |
| Fewest moves from (2, 3) to (6, 1) | 4 across + 2 down = 6 |
| Back to the start | difference of East and West steps + difference of North and South steps |
| Routes on a 2 × 2 street grid | 6 |
Watch out
- Writing (row, column) instead of (column, row).
- Moving the robot when it only turns: L and R do not change the cell.
- Turning the wrong way: a right turn from North faces East, not West.
Worked example
(a) On a street grid you walk from corner (0, 0) to corner (3, 4), moving only right (east) or up (north), one block at a time. How many different shortest routes are there? (b) On a grid of streets, a delivery robot goes 7 steps West, then 6 steps North, then 7 steps South, then 1 step South, then 1 step West. It can only move North, South, East or West. What is the fewest number of steps to get back to the start?
Working: (a) write at each corner the number of ways to reach it: the corner to its left plus the corner below; (b) it ends 8 West and 2 South of the start
Answer: (a) 35; (b) 10
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