java 移除字符串中的加号

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云中谁寄锦书来 2024-12-18 10:48:56

文章标签 java 移除字符串中的加号 LeetCode 魔法字典字典树字符串匹配 文章分类 Java 后端开发

题目描述

设计一个使用单词列表进行初始化的数据结构，单词列表中的单词互不相同。如果给出一个单词，请判定能否只将这个单词中一个字母换成另一个字母，使得所形成的新单词存在于你构建的字典中。

实现 MagicDictionary 类：

MagicDictionary() 初始化对象
void buildDict(String[] dictionary) 使用字符串数组 dictionary 设定该数据结构，dictionary 中的字符串互不相同
bool search(String searchWord) 给定一个字符串 searchWord ，判定能否只将字符串中一个字母换成另一个字母，使得所形成的新字符串能够与字典中的任一字符串匹配。如果可以，返回 true ；否则，返回 false 。

示例：

输入
["MagicDictionary", "buildDict", "search", "search", "search", "search"]
[[], [["hello", "leetcode"]], ["hello"], ["hhllo"], ["hell"], ["leetcoded"]]
输出
[null, null, false, true, false, false]
解释

MagicDictionary magicDictionary = new MagicDictionary();
 magicDictionary.buildDict(["hello", "leetcode"]);
 magicDictionary.search("hello"); // 返回 False
 magicDictionary.search("hhllo"); // 将第二个 'h' 替换为 'e' 可以匹配 "hello" ，所以返回 True
 magicDictionary.search("hell"); // 返回 False
 magicDictionary.search("leetcoded"); // 返回 False

来源：力扣（LeetCode）
链接：https://leetcode.cn/problems/implement-magic-dictionary

解题思路

第一种思路，直接使用MAP，将所有case都计算一遍，这个方法最终耗时过高放弃。

第二种思路，在查询的时候遍历字符串，如果check条件是有一个字符不相同，则返回true，否则重试，如果都不满足条件，返回false；

第三种思路，对第二种进行调整，提前记录长度和字符串的关系，根据长度来获取字符串，然后按照第二种思路执行，耗时有所下降

第四种思路，使用字典树，记录每个字符串的字典树；然后使用字符串匹配字典树；匹配条件：

如果已经到字符串结束位置，判断字典树已经结束，并且有被修改的记录。
如果字典树中有匹配的字符，则递归调用，如果结果为true，则直接返回true，否则进入下一步
如果字典树中没有匹配字符，则剔除当前字符所在位置后，找到一个新的存在的字符，做递归调用，并且将修改标记设置为true；

代码实现

第一种实现，直接使用MAP，将所有case都计算一遍

import java.util.HashMap;
import java.util.Map;

class MagicDictionary1 {

    Map<Integer, Map<String, String>> map;

    public MagicDictionary1() {
        this.map = new HashMap<>();
    }

    public void buildDict(String[] dictionary) {

        for (String s : dictionary) {
            Map<String, String> newMap = map.get(s.length());
            if (newMap == null) {
                map.put(s.length(), new HashMap<>());
                newMap = map.get(s.length());
            }

            for (int i = 0; i < s.length(); i++) {

                for (char c = 'a'; c <= 'z'; c++) {
                    if(s.charAt(i) == c) {
                        continue;
                    }
                    if (i == 0) {
                        newMap.put(c + s.substring(1), s);
                    } else if (i == s.length() - 1) {
                        newMap.put(s.substring(0, s.length() - 1) + c, s);
                    } else {
                        String s1 = s.substring(0, i) + c + s.substring(i + 1);
                        newMap.put(s1, s);
                    }
                }
            }
        }

    }

    public boolean search(String searchWord) {
        int length = searchWord.length();
        Map<String, String> newMap = map.get(length);
        if (newMap != null) {
            return newMap.get(searchWord) != null;
        }
        return false;
    }

第二种实现：

class MagicDictionary2 {

    String[] dictionary;

    public MagicDictionary2() {

    }

    public void buildDict(String[] dictionary) {
        this.dictionary = dictionary;
    }

    public boolean search(String searchWord) {
        for (String d : dictionary) {
            int length = searchWord.length();
            if (d.length() != length) {
                continue;
            }

            if (isOneDif(d, searchWord)) {
                return true;
            }
        }
        return false;
    }

    private boolean isOneDif(String d, String searchWord) {

        int dif = 0;
        for (int i = 0; i < d.length(); i++) {
            if (d.charAt(i) == searchWord.charAt(i)) {
                continue;
            } else {
                dif++;
            }
        }
        return dif == 1;
    }

    //["MagicDictionary", "buildDict", "search", "search", "search", "search"]
    //[[], [["hello","hallo","leetcode"]], ["hello"], ["hallo"], ["hell"], ["leetcodd"]]
    public static void main(String[] args) {
        MagicDictionary2 dictionary = new MagicDictionary2();
        dictionary.buildDict(new String[]{"hello", "hallo", "leetcode"});

        System.out.println(dictionary.search("leetcodd"));
    }
}

第三种实现：

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

class MagicDictionary3 {

    Map<Integer, List<String>> map;

    public MagicDictionary3() {
        map = new HashMap<>();
    }

    public void buildDict(String[] dictionary) {
        for (String d : dictionary) {
            int length = d.length();
            List<String> list = map.get(length);
            if (list == null) {
                list = new ArrayList<>();
                map.put(length, list);
            }
            list.add(d);
        }
    }

    public boolean search(String searchWord) {
        List<String> dictionary = map.get(searchWord.length());
        if (dictionary == null) {
            return false;
        }
        for (String d : dictionary) {
            if (isOneDif(d, searchWord)) {
                return true;
            }
        }
        return false;
    }

    private boolean isOneDif(String d, String searchWord) {

        int dif = 0;
        for (int i = 0; i < d.length(); i++) {
            if (d.charAt(i) == searchWord.charAt(i)) {
                continue;
            } else {
                dif++;
            }
        }
        return dif == 1;
    }

    //["MagicDictionary", "buildDict", "search", "search", "search", "search"]
    //[[], [["hello","hallo","leetcode"]], ["hello"], ["hallo"], ["hell"], ["leetcodd"]]
    public static void main(String[] args) {
        MagicDictionary3 dictionary = new MagicDictionary3();
        dictionary.buildDict(new String[]{"hello", "hallo", "leetcode"});

        System.out.println(dictionary.search("leetcodd"));
    }
}

第四种实现，字典树：

class MagicDictionary {

    Trie root;

    public MagicDictionary() {
        this.root = new Trie();
    }

    public void buildDict(String[] dictionary) {

        for (String dic : dictionary) {
            insert(dic, root);
        }

    }

    private void insert(String dic, Trie root) {

        for (int i = 0; i < dic.length(); i++) {
            char c = dic.charAt(i);
            int index = c - 'a';

            Trie newTrie = root.children[index];
            if (newTrie == null) {
                newTrie = new Trie();
                root.children[index] = newTrie;
            }
            if (i >= dic.length() - 1) {
                newTrie.isFinished = true;
            }
            root = newTrie;
        }

    }

    public boolean search(String searchWord) {

        return dfs(searchWord, root, 0, false);
    }

    private boolean dfs(String searchWord, Trie root, int position, boolean modified) {

        if (position >= searchWord.length()) {
            return root.isFinished && modified;
        }

        char c = searchWord.charAt(position);
        int index = c - 'a';

        Trie trie = root.children[index];

        if (trie != null) {
            if (dfs(searchWord, trie, position + 1, modified)) {
                return true;
            }
        }

        if (!modified) {
            for (int i = 0; i < 26; i++) {
                if (i != index && root.children[i] != null) {
                    if (dfs(searchWord, root.children[i], position + 1, true)) {
                        return true;
                    }
                }
            }
            return false;
        }
        return false;

    }

    static class Trie {
        boolean isFinished;
        Trie[] children;

        public Trie() {
            this.isFinished = false;
            this.children = new Trie[26];
        }

    }


    //["MagicDictionary", "buildDict", "search", "search", "search", "search"]
    //[[], [["hello","hallo","leetcode"]], ["hello"], ["hallo"], ["hell"], ["leetcodd"]]
    public static void main(String[] args) {
        MagicDictionary dictionary = new MagicDictionary();
        dictionary.buildDict(new String[]{"hello", "hallo", "leetcode"});

        System.out.println(dictionary.search("leetcodd"));
        System.out.println(dictionary.search("hello"));
    }