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Lc0657

05 August 2008

657 Judge Route Cycle

原题概述

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 

1

R
(Right), 
1

L
(Left), 
1

U
(Up) and 
1

D
(down). The output should be true or false representing whether the robot makes a circle.

Example 1:

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Input: "UD"
Output: true

Example 2:

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2

Input: "LL"
Output: false

题意和分析

找是否绕圈，有多少个U就得有多少个D，有多少个L就得有多少个R，跟20 - Valid Parentheses类似，那道题用stack来解，这个题更简单，两个计数器来看最后是否为0就行了。

代码

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class Solution {
    public boolean judgeCircle(String moves) {
        if (moves == null || moves.length() == 0) {
            return true;
        }
        int countH = 0, countV = 0;
        for (int i = 0; i < moves.length(); i++) {
            if (moves.charAt(i) == 'L') countH++;
            if (moves.charAt(i) == 'R') countH--;
            if (moves.charAt(i) == 'U') countV++;
            if (moves.charAt(i) == 'D') countV--;
        }
        return countH == 0 && countV == 0;
    }
}
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