Initially, there is a Robot at position (0, 0). Given a sequence of its moves, judge if this robot makes a circle, which means it moves back to the original place.
The move sequence is represented by a string. And each move is represent by a character. The valid robot moves are R (Right), L (Left), U (Up) and D (down). The output should be true or false representing whether the robot makes a circle.
Example 1:
Input: "UD" Output: true
Example 2:
Input: "LL" Output: false
Intuition
We can simulate the position of the robot after each command.
Algorithm
Initially, the robot is at (x, y) = (0, 0). If the move is 'U', the robot goes to (x, y-1); if the move is 'R', the robot goes to (x, y) = (x+1, y), and so on.
Complexity Analysis
Time Complexity: , where is the length of moves. We iterate through the string.
Space Complexity: . In Java, our character array is .
Analysis written by: @awice.