面试题58 - II. 左旋转字符串

你的名字 2023-02-19 05:25 6阅读 0赞

# 题目： #

[面试题58 - II. 左旋转字符串][58 - II.]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70]

# 题解： #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 1]

## 1. 题解一：字符串切片 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 2]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 3]

## 2. 题解二：列表遍历拼接 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 4]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 5]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 6]

## 3. 题解三：字符串遍历拼接 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 7]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 8]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 9]

## 4. 题解四：三步翻转法（优先） ##

算法思想：
    1. 第一步：先对前 n 个字符进行翻转；
    2. 第二步：然后对后面的部分进行翻转；
    3. 第三步：最后对整体进行翻转。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 10]  
**证明：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 11]

# 代码： #

## 1. 代码一：字符串切片 ##

// 方法1：字符串切片
    public static String reverseLeftWords(String s, int n) { 
        return s.substring(n, s.length()) + s.substring(0, n);
    }

## 2. 代码二：列表遍历拼接 ##

// 方法2：列表遍历拼接
    public static String reverseLeftWords(String s, int n) { 
        StringBuilder res = new StringBuilder();
        for(int i = n; i < s.length(); i++)
        { 
            res.append(s.charAt(i));
        }
        for(int i = 0; i < n; i++)
        { 
            res.append(s.charAt(i));
        }
        return res.toString();
    }

## 3. 代码三：字符串遍历拼接 ##

// 方法3：字符串遍历拼接
    public static String reverseLeftWords(String s, int n) { 
        String res = "";
        for(int i = n; i < s.length(); i++)
        { 
            res += s.charAt(i);
        }
        for(int i = 0; i < n; i++)
        { 
            res += s.charAt(i);
        }
        return res;
    }

## 4. 代码四：三步翻转法（优先） ##

public class 面试题58_2 { 
    
        // 方法4：三步翻转法
        public static String reverseLeftWords(String s, int n) { 
            char c[] = s.toCharArray();
            reverse(c, 0, n - 1); // 第一步：先对前 n 个字符进行翻转
            reverse(c, n, c.length - 1); // 第二步：然后对后面的部分进行翻转
            reverse(c, 0, c.length - 1); // 第三步：最后对整体进行翻转
            return String.valueOf(c);
        }
    
        public static void reverse(char c[], int i, int j)
        { 
            while(i < j)
            { 
                char temp = c[i];
                c[i] = c[j];
                c[j] = temp;
                i++;
                j--;
            }
        }
    
        public static void main(String[] args) { 
            String s1 = "abcdefg";
            int k1 = 2;
            String res1 = reverseLeftWords(s1, k1);
            System.out.println(res1);
    
            String s2 = "lrloseumgh";
            int k2 = 6;
            String res2 = reverseLeftWords(s2, k2);
            System.out.println(res2);
        }
    }

# 参考： #

1.  [面试题58 - II. 左旋转字符串（切片 / 列表 / 字符串，清晰图解）][58 - II. _ _ _ _]
2.  [java关于substring(a)与substring(a,b)的用法][java_substring_a_substring_a_b]
3.  [小技巧----“三步翻转法”][----]
4.  [字符串翻转练习—三步翻转法][Link 1]

# 效率分析： #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 12]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 13]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 14]

[58 - II.]: https://leetcode-cn.com/problems/zuo-xuan-zhuan-zi-fu-chuan-lcof/
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[58 - II. _ _ _ _]: https://leetcode-cn.com/problems/zuo-xuan-zhuan-zi-fu-chuan-lcof/solution/mian-shi-ti-58-ii-zuo-xuan-zhuan-zi-fu-chuan-qie-p/
[java_substring_a_substring_a_b]: https://blog.csdn.net/qq_38039015/article/details/82222063
[----]: https://blog.csdn.net/LF_2016/article/details/51549574
[Link 1]: https://blog.csdn.net/u010016196/article/details/45126853
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