LeetCode_单词的压缩编码_Array_M

820. 单词的压缩编码

  暴力..

class Solution {
    public int minimumLengthEncoding(String[] words) {
        String[] temp = new String[words.length];   // 不能压缩的字符串集合
        int size = 0, sum = 0;
        boolean isEnd = false;
        for (String s : words) {
            isEnd = false;
            for (int i = 0; i < size; i++) {
                if (temp[i].endsWith(s)) {    // 当前s属于一个已有的字符串的尾巴,啥事儿不干
                    isEnd = true;
                    break;
                }
                if (s.endsWith(temp[i])) {    // 已有字符串是当前s的尾巴,s替换掉原来的值
                    sum = sum - temp[i].length() + s.length();
                    temp[i] = s;
                    isEnd = true;
                    break;
                }
            }
            if (!isEnd) {   // 是一个新的
                temp[size++] = s;
                sum += s.length() + 1;
            }
        }
        return sum;
    }
}

别人的方法1：

class Solution {
    public int minimumLengthEncoding(String[] words) {
        // 花式删除重复尾巴重复的
        Set<String> set = new HashSet<>(Arrays.asList(words));
        for (String s : words) {
            for (int i = 1; i < s.length(); i++) {
                set.remove(s.substring(i));
            }
        }
        // 统计
        int sum = 0;
        for (String s : set) {
            sum += s.length() + 1;
        }
        return sum;
    }
}

别人的方法2：

class Solution {
    public int minimumLengthEncoding(String[] words) {
        // 从长到短的排序
        Arrays.sort(words, (s1, s2) -> s2.length() - s1.length());
        // 然后计算
        StringBuilder sb = new StringBuilder();
        for (String s : words) {
            if (!sb.toString().contains(s + "#")) {
                sb.append(s).append("#");
            }
        }
        return sb.length();
    }
}

Trie 字典树：

class Solution {
    public int minimumLengthEncoding(String[] words) {
        int len = 0;
        Trie trie = new Trie();
        // 先对单词列表根据单词长度由长到短排序
        Arrays.sort(words, (s1, s2) -> s2.length() - s1.length());
        // 单词插入trie，返回该单词增加的编码长度
        for (String word: words) {
            len += trie.insert(word);
        }
        return len;
    }
}

// 定义trie
class Trie {
    
    TrieNode root;
    
    public Trie() {
        root = new TrieNode();
    }

    public int insert(String word) {
        TrieNode cur = root;
        boolean isNew = false;
        // 倒着插入单词
        for (int i = word.length() - 1; i >= 0; i--) {
            int c = word.charAt(i) - 'a';
            if (cur.children[c] == null) {
                isNew = true; // 是新单词
                cur.children[c] = new TrieNode();
            }
            cur = cur.children[c];
        }
        // 如果是新单词的话编码长度增加新单词的长度+1，否则不变。
        return isNew? word.length() + 1: 0;
    }
}

// 定义trie的节点
class TrieNode {
    char val;
    TrieNode[] children = new TrieNode[26];

    public TrieNode() {}

    public TrieNode(char val) {
        this.val = val;
    }
}

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