题解 | #字符串变形#

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 
     * @param n int整型 
     * @return string字符串
     */
     public String trans (String s, int n) {
        // write code here
        if(n==0){
            return s;
        }
        char[] ch = new char[n];
        ch = s.toCharArray();
        for(int i=0;i<ch.length;i++){
            if(ch[i]>=97&&ch[i]<=122){
                ch[i] -=32;

            }else if(ch[i]>=65&&ch[i]<=90){
                ch[i]+=32;
            }
        }
        if(!s.contains(" ")){
            return new String(ch);
        }

        //先整体转
        ch = transfor(ch,0,n-1);
        
        //转换单词,定义两个指针找到单词
        int cur1 = 0;
        int cur2 = 0;
        while(cur2<n){
            if(ch[cur2]!=' '){
                cur2++;
            }else if(ch[cur2]==' '){
                //遇到空格反转
                transfor(ch,cur1,cur2-1);
                cur2++;
                cur1 = cur2;
            }
        }
        //遇到最后一个单词反转
        transfor(ch,cur1,cur2-1);
       
        
        return new String(ch);


    }
    public  char[] transfor(char[] ch,int l,int r){
        int s =l;
        int e =r;
        while(s<=e){
            char tmp=ch[s];
            ch[s] = ch[e];
            ch[e] = tmp;
            s++;
            e--;
        }
        return ch;
    }
}