Leetcode:657. Judge Route Circle (week 7)

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;    }};