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
public class Solution {
public boolean judgeCircle(String moves) {
if (moves == null)
return true;
int x = 0, y = 0;
for (int i=0; i<moves.length(); i++) {
char ch = moves.charAt(i);
if (ch == 'U')
y ++;
else if (ch == 'D')
y --;
else if (ch == 'L')
x --;
else if (ch == 'R')
x ++;
}
return x==0 && y==0;
}
}