package top.qaqaq.java.P475;

import org.junit.jupiter.api.Test;

/**
 * @author RichieZhang
 * @create 2022-10-23 下午 2:17
 */
public class StringDemo {

    /*
    将一个字符串进行反转。将字符串中指定部分进行反转。比如“abcdefg”反转为”abfedcg”
    
    方式一：转换为char[]
     */
    public String reverse(String str, int startIndex, int endIndex){

        if(str != null){
            char[] arr = str.toCharArray();
            for (int x = startIndex,y = endIndex;x < y;x++,y--){
                char temp = arr[x];
                arr[x] = arr[y];
                arr[y] = temp;
            }

            return new String(arr);
        }

        return null;
    }

    //方式二：使用String的拼接
    public String reverse1(String str, int startIndex, int endIndex){
        if(str != null){
            //第1部分
            String reverseStr = str.substring(0,startIndex);
            //第2部分
            for (int i = endIndex; i >= startIndex; i--){
                reverseStr += str.charAt(i);
            }
            //第3部分
            reverseStr += str.substring(endIndex + 1);

            return  reverseStr;

        }

        return null;
    }

    //方式三：使用StringBuffer/StringBuilder替换String
    public String reverse2(String str, int startIndex, int endIndex) {
        if (str != null) {
            StringBuilder builder = new StringBuilder(str.length());

            //第1部分
            builder.append(str.substring(0, startIndex));

            //第2部分
            for (int i = endIndex; i >= startIndex; i--) {
                builder.append(str.charAt(i));
            }

            //第3部分
            builder.append(str.substring(endIndex + 1));

            return builder.toString();
        }

        return null;
    }

    @Test
    public void testReverse(){
        String str = "abcdefg";
        String reverse = reverse(str, 2, 5);
        String reverse1 = reverse1(str, 2, 5);
        String reverse2 = reverse2(str, 2, 5);
        System.out.println(reverse);
        System.out.println(reverse1);
        System.out.println(reverse2);
    }
}