题目：151. 反转字符串中的单词
题目链接：https://leetcode.cn/problems/reverse-words-in-a-string/description/
思路：1. 去除字符串的首尾空格，中间保留一个空格
2. 整个字符串全部反转
3. 根据空格，反转字符串中的单个单词
代码：
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public String reverseWords(String s) {//1. 去除首位以及中间多余空格StringBuilder sb=removeSpace(s);// 2.反转整个字符串reverseString(sb, 0, sb.length() - 1);// 3.反转各个单词reverseEachWord(sb);return sb.toString();}private StringBuilder removeSpace(String s){int start=0;int end=s.length()-1;while(start<=end && s.charAt(start)==' ') start++;while(start<=end && s.charAt(end)==' ')end--;StringBuilder sb=new StringBuilder();while(start<=end){char c=s.charAt(start);if(c!=' ' || sb.charAt(sb.length()-1)!=' '){ // 重点 单词之间保留1个空格sb.append(c);}start++;}return sb;}/*** 反转字符串指定区间[start, end]的字符*/public void reverseString(StringBuilder sb, int start, int end) {// System.out.println("ReverseWords.reverseString() called with: sb = [" + sb + "], start = [" + start + "], end = [" + end + "]");while (start < end) {char temp = sb.charAt(start);sb.setCharAt(start, sb.charAt(end));sb.setCharAt(end, temp);start++;end--;}// System.out.println("ReverseWords.reverseString returned: sb = [" + sb + "]");}private void reverseEachWord(StringBuilder sb) {int start = 0;int end = 1; //end作为每个单词的分割条件int n = sb.length();while (start < n) {while (end < n && sb.charAt(end) != ' ') {end++;}reverseString(sb, start, end - 1);start = end + 1;end = start + 1;}}