LeetCode Judge Route Circle

原题链接在这里：https://leetcode.com/problems/judge-route-circle/description/

题目：

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

题解：

判断'U'和'D' && 'R'和 'L'的个数是否相同.

Time Complexity: O(moves.length()). Space: O(1).

AC Java:

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