LeetCode - 657. Judge Route Circle

最新推荐文章于 2019-09-27 14:16:07 发布

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最新推荐文章于 2019-09-27 14:16:07 发布

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原文链接：http://www.cnblogs.com/wxisme/p/7366468.html

本文介绍了一个简单的算法，用于判断一个机器人是否能通过一系列指令回到起始位置(0,0)。该算法通过解析输入字符串中的指令（'U'向上、'D'向下、'L'向左、'R'向右），计算最终位置坐标，以此来判断机器人是否完成了一个闭环。

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;
    }
}