> ## Documentation Index
> Fetch the complete documentation index at: https://leetcode-py.wisl.dev/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> leetcode-py is a Python LeetCode practice environment generator with one CLI: lcpy. It is not a service or platform.
> Each problem is a directory under leetcode/ with README.md, solution.py, test_solution.py, helpers.py, and playground.ipynb. lcpy gen creates them from JSON templates bundled with the package.
> Examples are backed by tests; copy them verbatim.

# Robot Return to Origin Python Solution

> Tested Python solution for LeetCode 657 with 32 pytest cases. Generate a practice environment with lcpy.

LeetCode 657, [Easy](/catalog/easy). Topics: [String](/catalog/topics/string), [Simulation](/catalog/topics/simulation). [View on LeetCode](https://leetcode.com/problems/robot-return-to-origin/description/).

Generate this problem as a practice environment: tested reference solution, 32 [parametrized pytest cases](/practice/testing), and a playground notebook:

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -n 657   # by problem number
lcpy gen -s robot_return_to_origin   # by problem name
```

## Problem

There is a robot starting at the position `(0, 0)`, the origin, on a 2D plane. Given a sequence of its moves, judge if this robot **ends up at** `(0, 0)` after it completes its moves.

You are given a string `moves` that represents the move sequence of the robot where `moves[i]` represents its `i<sup>th</sup>` move. Valid moves are `'R'` (right), `'L'` (left), `'U'` (up), and `'D'` (down).

Return `true` *if the robot returns to the origin after it finishes all of its moves, or* `false` *otherwise*.

**Note**: The way that the robot is "facing" is irrelevant. `'R'` will always make the robot move to the right once, `'L'` will always make it move left, etc. Also, assume that the magnitude of the robot's movement is the same for each move.

### Examples

```
Input: moves = "UD"
Output: true
Explanation: The robot moves up once, and then down once. All moves have the same magnitude, so it ended up at the origin where it started. Therefore, we return true.
```

```
Input: moves = "LL"
Output: false
Explanation: The robot moves left twice. It ends up two "moves" to the left of the origin. We return false because it is not at the origin at the end of its moves.
```

### Constraints

* 1 \<= moves.length \<= 2 \* 10^4
* moves only contains the characters 'U', 'D', 'L' and 'R'.

## Solution

Reference implementation from [solution.py on GitHub](https://github.com/wislertt/leetcode-py/blob/main/leetcode/robot_return_to_origin/solution.py), full suite in [test\_solution.py](https://github.com/wislertt/leetcode-py/blob/main/leetcode/robot_return_to_origin/test_solution.py):

```python theme={"theme":{"light":"github-light","dark":"github-dark"}}
class Solution:
    # Time: O(n)
    # Space: O(1)
    def judge_circle(self, moves: str) -> bool:
        x = 0
        y = 0
        for move in moves:
            if move == "U":
                y += 1
            elif move == "D":
                y -= 1
            elif move == "L":
                x -= 1
            else:
                x += 1
        return x == 0 and y == 0
```

## Complexity

| Time | Space |
| - | - |
| O(n) | O(1) |

## Tags


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