day09--151.翻转字符串里的单词+ 右旋字符串

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一、151.翻转字符串里的单词

题目链接：https://leetcode.cn/problems/reverse-words-in-a-string/
文章讲解：https://programmercarl.com/0151.%E7%BF%BB%E8%BD%AC%E5%AD%97%E7%AC%A6%E4%B8%B2%E9%87%8C%E7%9A%84%E5%8D%95%E8%AF%8D.html#%E7%AE%97%E6%B3%95%E5%85%AC%E5%BC%80%E8%AF%BE
视频讲解：https://www.bilibili.com/video/BV1uT41177fX

1.1 初见思路

1.先翻转每个单词，再翻转整个字符串
2.消除多余空格

1.2 具体实现

class Solution {public String reverseWords(String s) {//1.把字符串去掉多余空格StringBuilder stringBuilder = removeMoreSpace(s);//2.翻转整个字符串reverseWholeStr(stringBuilder);//3.翻转每个单词reverAllWord(stringBuilder);return stringBuilder.toString();}public  StringBuilder removeMoreSpace(String s){StringBuilder stringBuilder = new StringBuilder();int left =0;int right = s.length()-1;while(s.charAt(left)==' '){left++;}while(s.charAt(right)==' '){right--;}for(int i=left;i<=right;i++){//如果是空格，则跳过,得保留一个空格的if(s.charAt(i)==' '){if(s.charAt(i-1)!=' '){stringBuilder.append(' ');}continue;}// System.out.println("i="+i+"::::对应的s"+s.charAt(i));stringBuilder.append(s.charAt(i));}return stringBuilder;}public  void reversePartStr(StringBuilder sb,int left ,int right){while(left<right){char temp = sb.charAt(right);sb.setCharAt(right,sb.charAt(left));sb.setCharAt(left,temp);left++;right--;}}public  void reverseWholeStr(StringBuilder stringBuilder){reversePartStr(stringBuilder, 0, stringBuilder.length() - 1);System.out.println(stringBuilder);}public  void  reverAllWord(StringBuilder sb){int start = 0;int end = 1;int n = sb.length();while (start < n) {while (end < n && sb.charAt(end) != ' ') {end++;}reversePartStr(sb, start, end - 1);start = end + 1;end = start + 1;}}
}

1.3 重难点

二、右旋字符串

题目链接：https://kamacoder.com/problempage.php?pid=1065
文章讲解：https://programmercarl.com/kamacoder/0055.%E5%8F%B3%E6%97%8B%E5%AD%97%E7%AC%A6%E4%B8%B2.html#%E5%85%B6%E4%BB%96%E8%AF%AD%E8%A8%80%E7%89%88%E6%9C%AC
视频讲解：https://www.bilibili.com/video/BV12A4y1Z7LP

2.1 初见思路

1.翻转整个字符串
2.反转前一段字符串
3.反转后一段字符串

2.2 具体实现

public class Main {public static void main(String[] args) {Scanner in = new Scanner(System.in);int n = Integer.parseInt(in.nextLine());String s = in.nextLine();int len = s.length();  //获取字符串长度char[] chars = s.toCharArray();reverseString(chars, 0, len - 1);  //反转整个字符串reverseString(chars, 0, n - 1);  //反转前一段字符串，此时的字符串首尾尾是0,n - 1reverseString(chars, n, len - 1);  //反转后一段字符串，此时的字符串首尾尾是n,len - 1System.out.println(chars);}public static void reverseString(char[] ch, int start, int end) {//异或法反转字符串，参照题目 344.反转字符串的解释while (start < end) {ch[start] ^= ch[end];ch[end] ^= ch[start];ch[start] ^= ch[end];start++;end--;}}
}