题解 | #字符串变形#

package main

import "fmt"

/**
 * 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
 */
func trans(s string, n int) string {
	if n == 0 {

	}
	var r = []rune(s)
    // 全部翻转
	reserve(r, 0, n-1)

    // 大小写互换
	for i := 0; i < n; i++ {
		if r[i] == ' ' {
			continue
		}
		if r[i] >= 'A' && r[i] <= 'Z' {
			r[i] = r[i] - 'A' + 'a'
		} else {
			r[i] = r[i] - 'a' + 'A'
		}
	}

    // 单个单词翻转
    var begin,end int
    for i:=0; i < n; i ++ {
        if r[i] == ' ' {
            end = i - 1
            if end > begin {
                reserve(r, begin, end)
            }
            begin = i+1
        }else if i == n-1 {
            end = i
            if end > begin {
                reserve(r, begin, end)
            }
        } 
        
        continue
    }




	return string(r)
}

func reserve(s []rune, start, end int) {

	for start < end {
		temp := s[start]
		s[start] = s[end]
		s[end] = temp
		start++
		end--
	}

}