字符串反序

题目: 字符串反序输出

输入:today is a good day!

输出:day! good a is today

思路:

1.提取构造反序输出模板

如果是空字符，则用0代替，如果不是空字符，则用1代替.

2.提取其中的单个字符串

通过去除前后空格，然后递归判断内部是否还有空字符，如果有递归，否则返回.构造字符串序列.

3.将模板与提取后的字符串适配

将字符串序列与模板适配，0和1用字符序列替换，得到反转序列.

/**
 * 字符串反转
 *
 * @author renwei
 *
 */
public class ReserverString
{
    private static final char ZERO = '0';
    private static final char ONE = '1';
    private static final char SPACE = ' ';

    /**
     * 反转字符串
     *
     * @param input
     *            输入字符串
     * @return 反转后的字符串
     */
    private static String reserverString(String input)
    {
        final StringBuilder strBuilder = new StringBuilder();
        final String template = constructTemplate(input);
        extractStr(input, strBuilder);
        return adapterTemplate(strBuilder, template);
    }

    /**
     * 构造模板
     *
     * @param input
     *            输入字串
     * @return 反转后模板
     */
    private static String constructTemplate(String input)
    {
        final StringBuilder base = new StringBuilder();
        for (int index = 0; index < input.length(); index++)
        {
            if (input.charAt(index) == SPACE)
            {
                base.append(ZERO);
            }
            else
            {
                base.append(ONE);
            }
        }
        return base.reverse().toString();
    }

    /**
     * 提取单个字串
     *
     * @param value
     *            输入字串
     * @param result
     *            收集实际字串
     */
    private static void extractStr(String value, StringBuilder result)
    {
        String trimStr = value.trim();
        final int index = trimStr.indexOf(" ");
        if (index == -1)
        {
            result.append(trimStr);
        }
        else
        {
            final String baseStr = trimStr.substring(0, index);
            final String rest = trimStr.substring(index, trimStr.length());
            extractStr(rest, result);
            result.append(baseStr);
        }
    }

    /**
     * 适配模板与字符串
     *
     * @param value
     * @param template
     * @return
     */
    private static String adapterTemplate(StringBuilder value, String template)
    {
        final StringBuilder result = new StringBuilder();
        int base = 0;
        for (int index = 0; index < template.length(); index++)
        {
            if (template.charAt(index) == ZERO)
            {
                result.append(" ");
            }
            else if (template.charAt(index) == ONE)
            {
                result.append(value.toString().charAt(base++));
            }
        }
        return result.toString();
    }

    /**
     * 测试
     *
     * @param args
     */
    public static void main(String[] args)
    {
        String input = " today is a good day! ";
        System.out.println("input==" + input);
        final String result = reserverString(input);
        System.out.println("result==" + result);
    }
}

结果输出:

input== today is a good day!
result== day! good a is today