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 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

容易想到每一步为一个向量，最终若向量之和为0则回到原点，简单计数即可解决

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