Leetcode 151. Reverse Words in a String

最新推荐文章于 2024-01-04 11:20:32 发布

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最新推荐文章于 2024-01-04 11:20:32 发布

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分类专栏： Leetcode String

本文链接：https://blog.youkuaiyun.com/u011094114/article/details/54842465

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本文介绍了一个Java方法，用于翻转字符串中的单词，并详细展示了如何处理空格、边界情况及内部实现细节。

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public class Solution {
    public String reverseWords(String s) {
        if (s == null || s.length() == 0) return "";
        
        StringBuilder str = new StringBuilder(s);
        StringBuilder ret = new StringBuilder();
        
        reverse(0, str.length()-1, str);
        
        // trim leading and tailing spaces
        int st = 0, ed = str.length()-1;
        while (st < str.length() && str.charAt(st) == ' ') st++;
        while (ed >= 0 && str.charAt(ed) == ' ') ed--;
        if (st == ed+str.length()+1) return ret.toString();
        str = new StringBuilder(str.substring(st, ed+1));
        
        // trime middle spaces
        st = 0; ed = 0;
        while (st < str.length()) {
            while (st<str.length() && str.charAt(st) == ' ') st++;
            ed = st;
            while (ed<str.length() && str.charAt(ed) != ' ') ed++;
            reverse(st, ed-1, str);
            ret.append(str.substring(st, ed));
            ret.append(' ');
            st = ed;
        }
        
        // remove the last blankspace
        return ret.substring(0, ret.length()-1);
    }
    
    public static void reverse(int lo, int hi, StringBuilder str) {
        while (lo < hi) {
            char tmp = str.charAt(lo);
            str.setCharAt(lo, str.charAt(hi));
            str.setCharAt(hi, tmp);
            lo++;
            hi--;
        }
    }
}