[程序人生]: 反转一个句子

题目：

反转一个句子，要求句子中的每个单子都被反转，但单词本身不被反转

如：I am a Boy! 反转为：Boy! a am I

思路：左旋转处理

1. 将整个句子的所有字符统一反转

2. 根据空格，阶段单词，再反转每一个单词

代码：

    public static String ReversalString(String StrInput){
        
        /*
        char[] charTemp = StrInput.toCharArray();

        int iFlagBegin = 0;
        int iFlagEnd = charTemp.length-1;
        
        while(iFlagBegin < iFlagEnd){
            char Temp = charTemp[iFlagBegin];
            charTemp[iFlagBegin] = charTemp[iFlagEnd];
            charTemp[iFlagEnd] = Temp;
            
            iFlagBegin++;
            iFlagEnd--;
        }
        
        return String.valueOf(charTemp);
        */
        String strResult = "";
        
        for(int i =0;i<StrInput.length();i++ ){
            strResult =StrInput.substring(i,i+1) + strResult;
        }
        return strResult;
    }
    
    public static String ReversalSentence(String Initial){
        String strResult = "";
        String strReversalAll = ReversalString(Initial);
        
        int iFlag = 0;
        for(int i = 0; i < strReversalAll.length(); i++){
            if(strReversalAll.substring(i, i+1).equals(" ")){
                if(i >= iFlag){
                    strResult += ReversalString(strReversalAll.substring(iFlag,i)) + " ";
                    iFlag = i+1;
                }
            }
            
            if(i == strReversalAll.length() -1){
                if(strReversalAll.substring(i,i+1).equals(" ")){
                    strResult = strResult.substring(0, strResult.length()-1);
                }
                else{
                    strResult += ReversalString(strReversalAll.substring(iFlag,i+1));
                }
            }
        }
        
        
        return strResult;
    }

分析：注意翻转字符串的函数，用注释中的写法高效！

思路二：查找空格，直接按照单词为集合反转

    public static String ReversalSentence(String Initial){

        String strResult ="";
        int iFlag = 0;
        for(int i = 0; i < Initial.length(); i++){
            if(i == Initial.length() -1){
                strResult = Initial.substring(iFlag,i+1) + " "  + strResult ;
            }
            
            if(Initial.substring(i, i+1).equals(" ")){
                if(i >= iFlag){
                    if(iFlag == 0){
                        strResult = Initial.substring(iFlag,i) + strResult;
                    }else{
                        strResult = Initial.substring(iFlag,i) + " " + strResult;
                    }
                    
                    iFlag = i+1;
                }
            }
        }
        
        
        return strResult;
    }