剑指 Offer 58 - I. 翻转单词顺序

https://leetcode-cn.com/problems/fan-zhuan-dan-ci-shun-xu-lcof/

• 双指针法

public String reverseWords(String s) {
    s = s.trim();//删除首尾空格
    int i=s.length()-1,j=s.length()-1;
    StringBuilder sb = new StringBuilder();
    while (i>=0){
        while (i>=0&&s.charAt(i)!=' ')i--;//搜索首个空格
        sb.append(s.substring(i+1,j+1)+" ");
        while (i>=0&&s.charAt(i)==' ')i--;
        j=i;
    }
    if(sb.length()!=0){
        sb.deleteCharAt(sb.length()-1);//删除最后一个空格
    }

    return sb.toString();
}

• 库函数

String[] ss = s.trim().split(" ");
StringBuilder sb = new StringBuilder();
for(int i=ss.length-1;i>=0;i--){
    if(ss[i].equals(""))continue;
    sb.append(ss[i]+' ');
}
return sb.toString().trim();