《程序员代码面试指南》第五章 字符串问题 找到被指的新类型字符

题目

找到被指的新类型字符

java代码

package com.lizhouwei.chapter5;

/**
 * @Description: 找到被指的新类型字符
 * @Author: lizhouwei
 * @CreateDate: 2018/4/25 21:20
 * @Modify by:
 * @ModifyDate:
 */
public class Chapter5_19 {

    public String pointNewChar(String str, int k) {
        if (str == null || k < 0 || k > str.length()) {
            return null;
        }
        char[] chars = str.toCharArray();
        int count = 0;
        for (int i = k - 1; i > -1; i--) {
            if (Character.isLowerCase(chars[i])) {
                break;
            }
            count++;
        }
        if ((count & 1) == 1) {
            return str.substring(k - 1, k + 1);
        }
        if (Character.isLowerCase(chars[k])) {
            return String.valueOf(chars[k]);
        } else {
            return str.substring(k, k + 2);
        }
    }

    //测试
    public static void main(String[] args) {
        Chapter5_19 chapter = new Chapter5_19();
        String str = "aaABCDEcBCg";
        String result = chapter.pointNewChar(str, 7);
        System.out.println("aaABCDEcBCg 第7位的新字符为：" + result);
    }
}

结果