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.
Copy the code

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.
Copy the code

Can a point return to its original position after a number of moves?

We only need to judge two conditions:

  • The number of moves to the left is the same as the number of moves to the right
  • Is the number of moves up the same as the number of moves down

So we just have to figure out how many steps left, right, up, and down.

Python code:

class Solution(object) :
    def judgeCircle(self, moves) :
        """ :type moves: str :rtype: bool """
        moves_length = len(moves)
        L_count = 0
        R_count = 0
        U_count = 0
        D_count = 0
        for i in range(moves_length):
            if moves[i] == 'L':
                L_count = L_count + 1
            elif moves[i] == 'R':
                R_count = R_count + 1
            elif moves[i] == 'U':
                U_count = U_count + 1
            elif moves[i] == 'D':
                D_count = D_count + 1
        
        if L_count == R_count and U_count == D_count:
            return True
        else:
            return False
Copy the code

C + + code:

class Solution {
public:
    bool judgeCircle(string moves) {
        int moves_length = moves.length(a);int L_count = 0;
        int R_count = 0;
        int U_count = 0;
        int D_count = 0;
        for(int i = 0; i < moves_length; i++){
            if(moves[i] == 'L'){
                L_count++;
            }
            else if(moves[i] == 'R'){
                R_count++;
            }
            else if(moves[i] == 'U'){
                U_count++;
            }
            else if(moves[i] == 'D'){ D_count++; }}if(L_count == R_count && U_count == D_count){
            return true;
        }
        return false; }};Copy the code