Leetcode:657. Judge Route Circle (week 7)-优快云博客

本文链接：https://blog.youkuaiyun.com/csdn_cinderella/article/details/78248511

本文介绍了一个简单算法，用于判断机器人在给定移动序列后是否回到了初始位置。通过遍历字符串并更新坐标来实现。

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Description:

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

解题思路分析

本题判断移动后是否回到原点，解题思路很简单：首先声明两个int型变量x,y作为坐标，遍历字符串若为R则x++,若为L则x–,若为U则y++,若为D则y–；遍历结束后比较x,y是否为0 =，均为0则返回true。
时间复杂度为O(n),n为字符串长度。

代码

class Solution {
public:
    bool judgeCircle(string moves) {
        int x = 0, y = 0;
        for (std::string::iterator it=moves.begin(); it!=moves.end(); ++it) {
            if (*it == 'R') {
                x++;
            } else if (*it == 'L') {
                x--;
            } else if (*it == 'U') {
                y++;
            } else if (*it == 'D') {
                y--;
            }
        }
        if (x == 0 && y == 0) return true;
        return false;
    }
};