题解 | #牛群的配对#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param s string字符串 
     * @return bool布尔型
     */
    public boolean isValidPairing (String s) {
        // write code here

        if(s == null ) return true;
        if(0 == s.length()) return false;
        char[] charStack = new char[s.length()];
        int charCount = 0;

        for(int i = 0;i<s.length();i++){
            char c = s.charAt(i);
            if(0 == charCount) {
                charStack[charCount++] = c;
            } else {
                char cacheTopChar = charStack[charCount - 1];
                if(matchPaireRule(cacheTopChar,c)){
                    charStack[charCount-1] = 0;
                    charCount --;
                } else {
                    charStack[charCount++] = c;
                }
            }
        }


        return charCount == 0;
    }

    private boolean matchPaireRule(char leftC ,char rightC){
        if( 'A' == leftC  && 'B' == rightC
            // || 'B' == leftC && 'A' == rightC 
            || 'C'==leftC && 'D'==rightC
            // || 'D'==leftC && 'C' == rightC
            ){
            return true;
        } else {
            return false;
        }
    }

}

感觉这道题有歧义，

BADC 被认为是符合匹配规则的了