657. Judge Route Circle

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 represented 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

这个题很简单，就是判断各种拐弯时候能不能绕回来。 直接上代码吧。 

class Solution {public:    bool judgeCircle(string moves) {        if (moves.length() == 0) return true;        if (moves.length() % 2 == 1) return false;        int offset_x = 0;        int offset_y = 0;        for (int i = 0; i < moves.length(); i++) {            if (moves[i] == 'U') {                offset_y++;            } else if (moves[i] == 'D') {                offset_y--;            } else if (moves[i] == 'L') {                offset_x--;            } else if (moves[i] == 'R') {                offset_x++;            } else {                i++;            }        }        return offset_x == 0 && offset_y == 0 ? true : false;    }};