[學習筆記] leetcode 843. 猜猜這個單詞

import java.util.ArrayList;
import java.util.List;

public class Solution {
    int[][] H; // H[i][j]表示第i個和第j個字符串相同字母&位置的個數

    public void findSecretWord(String[] wordlist, Master master) {
        int N = wordlist.length;
        H = new int[N][N];
        for (int i = 0; i < N; ++i) {
            for (int j = i; j < N; ++j) {
                int match = 0;
                for (int k = 0; k < 6; ++k) {
                    if (wordlist[i].charAt(k) == wordlist[j].charAt(k))
                        match++;
                }
                H[i][j] = H[j][i] = match;
            }
        }
        List<Integer> possible = new ArrayList(); // 可能的詞
        List<Integer> path = new ArrayList(); // 已比較過的詞
        for (int i = 0; i < N; ++i) {
            possible.add(i);
        }

        while (!possible.isEmpty()) {
            int guess = solve(possible, path); // 獲取下一個用於猜測的詞的索引
            int matches = master.guess(wordlist[guess]);
            if (matches == wordlist[0].length()) {
                return;
            }
            List<Integer> possible2 = new ArrayList();
            for (Integer j : possible) {
                if (H[guess][j] == matches) { // 如果一個單詞已經匹配了matcher位，那麼有可能全部匹配的單詞至少要和當前這個單詞有matcher位相同
                    possible2.add(j);
                }
            }
            possible = possible2;
            path.add(guess);
        }

    }

    public int solve(List<Integer> possible, List<Integer> path) {
        // 如果只有1個或兩個單詞了，就直接返回第一個
        if (possible.size() <= 2) {
            return possible.get(0);
        }
        List<Integer> ansgrp = possible;
        int ansguess = -1;

        // 找出沒有猜過的詞中，和possible中其他詞匹配相同個數字符時，能匹配最多個詞的那個詞
        for (int guess = 0; guess < H.length; ++guess) {
            if (!path.contains(guess)) { // 排除已猜過的單詞
                ArrayList<Integer>[] groups = new ArrayList[7];
                // i < 7的原因是兩個詞匹配的字符個數可能是[0,6]
                // groups表示和guess所在的詞匹配的字符分別是[0,6]的詞的list
                for (int i = 0; i < 7; ++i) {
                    groups[i] = new ArrayList<Integer>();
                }
                for (Integer j : possible) {
                    if (j != guess) { // 不能是詞自己和自己比
                        groups[H[guess][j]].add(j);
                    }
                }
                ArrayList<Integer> maxgroup = groups[0];
                // 選出groups中list最長的那個list
                for (int i = 0; i < 7; ++i) {
                    if (groups[i].size() > maxgroup.size()) {
                        maxgroup = groups[i];
                    }
                }

                if (maxgroup.size() < ansgrp.size()) {
                    ansgrp = maxgroup;
                    ansguess = guess;
                }
            }
        }

        return ansguess;
    }

}

interface Master {
    public int guess(String word);
}