leetCode题解 寻找运动环

1、题目描述

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.

题目的意思是，如果一个可以上下左右运动，分别记做 ‘U’ ,’D’，‘L’，‘R’。将一个机器人的运动序列记做一个string ,根据这个string 判断机器人是否回到了原点。

2、问题分析

特例是机器人没有动，即string的长度是0,那么机器人就在原位。

机器人回到原位的条件是，上下运动的步数相等 并且 左右运动的步数相等。遍历一次string ，分别记录上下左右运动的次数，然后比较每个方向上运动的次数。如果  R == L  &&  U  == D  ,那么机器人回到了原点。

3、代码

  if(moves.size() == )
             return true;         int u = ;
         int d = ;
         int l = ;
         int r = ;         int i = ;
         while(i < moves.size())
         {
             switch (moves[i])
             {
                 case 'U':
                     ++u;
                     break;
                 case 'D':
                     ++d;
                     break;
                 case 'L':
                     ++l;
                     break;
                 case 'R':
                     ++r;
                     break;
                 default:
                     break;
             }
             i++;
         }         if(u == d && l == r)
             return true;         return false;