JudgeRouteCircle657.java

/**
 * 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 JudgeRouteCircle657 {
    public boolean judgeCircle(String s) {
        if (s == null || s.length() == 0) return true;
        char[] moves = s.toCharArray();
        int x = 0;
        int y = 0;
        for (int i=0; i<s.length(); i++) {
            switch (moves[i]) {
                case 'U': y--; break;
                case 'D': y++; break;
                case 'L': x--; break;
                case 'R': x++;
            }
        }
        return x == 0 && y == 0;
    }
}