13-challenge

Challenge 13

The elves at the North Pole have created a special robot 🤖 that helps Santa Claus distribute gifts inside a large warehouse. The robot moves on a 2D plane and we start from the origin (0, 0).

We want to know if, after executing a series of movements, the robot returns to exactly where it started.

The robot's basic commands are:

• L: Move to the left.
• R: Move to the right.
• U: Move upwards.
• D: Move downwards.

But it also has certain modifiers for the movements:

• *: The movement is done with double intensity (e.g., *R means RR)
• !: The next movement is inverted (e.g., R!L is considered as RR)
• ?: The next movement is done only if it hasn't been done before (e.g., R?R means R)

You must return:

• true: if the robot returns exactly to where it started.
• [x, y]: if the robot does not return to where it started, return the position where it stopped.

Note

When the movement is inverted with ! the inverted movement is counted and not the original one. For example, !U?U inverts the U movement, so it counts as having done the D movement but not the U. Thus, !U?U translates to D?U, and therefore, the final U movement is done.

isRobotBack('R') // Expected result: [1, 0]
isRobotBack('RL') // Expected result: true
isRobotBack('RLUD') // Expected result: true
isRobotBack('*RU') // Expected result: [2, 1]
isRobotBack('R*U') // Expected result: [1, 2]
isRobotBack('LLL!R') // Expected result: [-4, 0]
isRobotBack('R?R') // Expected result: [1, 0]
isRobotBack('U?D') // Expected result: true
isRobotBack('R!L') // Expected result: [2,0]
isRobotBack('U!D') // Expected result: [0,2]
isRobotBack('R?L') // Expected result: true
isRobotBack('U?U') // Expected result: [0,1]
isRobotBack('*U?U') // Expected result: [0,2]
isRobotBack('U?D?U') // Expected result: true

// Step-by-step examples...

isRobotBack('R!U?U') // Expected result: [1,0]
/**
 * 0: 'R'  => moves to the right.
 * 1: '!U' => inverts and becomes 'D'.
 * 2: '?U' => moves upwards, because the 'U' movement hasn't been done yet.
 */

isRobotBack('UU!U?D') // Expected result: [0,1]
/**
 * 0: 'U'  => moves upwards.
 * 1: 'U'  => moves upwards.
 * 2: '!U' => inverts and becomes 'D'.
 * 3: '?D' => does not move, since the 'D' movement has already been done.
 */

Solutions

• Python
• JavaScript
• TypeScript

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