Q657 Robot Return to Origin

Robot Return to Origin

Question

There is a robot starting at 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.

The move sequence is represented by a string, and the character moves[i] represents its ith move. Valid moves are R (right), L (left), U (up), and D (down). If the robot returns to the origin after it finishes all of its moves, return true. Otherwise, return false.

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.

Example 1:

Input: "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.

Example 2:

Input: "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.

Approach 1: Hash Set

Intuition and Algorithm

We can transform each word into it's Morse Code representation.

After, we put all transformations into a set seen, and return the size of the set.

class Solution(object):
    def judgeCircle(self, moves):
        Return=[0,0]
        for i in moves:
            if i=='U':
                Return[0] += 1
            elif i=='D':
                Return[0] -= 1
            elif i == 'L':
                Return[1] += 1
            elif i == 'R':
                Return[1] -= 1
        return not(bool(Return[0]) or bool(Return[1]))


def main():
    Action=['U','D']
    solution=Solution().judgeCircle(Action)
    print(solution)


if __name__ == "__main__":
    main()

Complexity Analysis

• Time Complexity: O(n), where n is the amount of the movents in moves.
• Space Complexity: O(1).
• Runtime: 88 ms, faster than 68.89% of Python online submissions for Robot Return to Origin.
• Memory Usage: 12.1 MB, less than 35.59% of Python online submissions for Robot Return to Origin.