Problem

Several people are playing the game of English word chain where each player takes turns saying a word that must begin with the last letter of the previous word. Here are the rules:

1. Players take turns in a sequence from 1 to n.
2. After the last player, it starts again with the first player.
3. The word must start with the last letter of the word the previous player said.
4. A word cannot be repeated.
5. A word must be more than one letter.

For example, if 3 people are playing:

• tank → kick → know → wheel → land → dream → mother → robot → tank
  The game progresses as follows:
• Player 1: tank
• Player 2: kick
• Player 3: know
• Player 1: wheel (continues…)

The game ends when a player repeats a word previously said or says a word that does not follow the rule of starting with the last letter of the previous word.

Given the number of players n and the list of words words spoken in order, the task is to determine the first player to be disqualified and on which turn they are disqualified. If no player is disqualified based on the provided words, return [0, 0].

Constraints

• The number of players n is a natural number between 2 and 10.
• words is an array of words used in the game, its length is between n and 100.
• Each word’s length is between 2 and 50 characters.
• All words consist of lowercase English letters.
• The meaning of the words is not considered in this game.

Example

Explanation of Examples

• Example 1:
  • With 3 players, the sequence of words goes as: Player 1: tank, wheel, mother; Player 2: kick, land, robot; Player 3: know, dream, tank. Player 3 repeats the word “tank” which was already said, resulting in their disqualification on their third turn.
• Example 2:
  • 5 players participate, and the sequence goes smoothly without any repetitions or rule violations, resulting in no disqualifications.
• Example 3:
  • With 2 players, Player 1 fails to follow the sequence properly on their third turn by saying “now,” which does not start with the required letter from the previous word, leading to their disqualification.

How to Approach?

step1.

Code

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import java.util.HashSet;
import java.util.Set;

public class Solution {
    public int[] solution(int n, String[] words) {
        Set<String> seenWords = new HashSet<>();
        int player = 0, turn = 0;
        
        // Initialize with the first word
        String lastWord = words[0];
        seenWords.add(lastWord);

        for (int i = 1; i < words.length; i++) {
            String currentWord = words[i];
            player = (i % n) + 1;
            turn = (i / n) + 1;
            
            // Check if the word is correct: not repeated and starts with the last character of the last word
            if (seenWords.contains(currentWord) ||currentWord.length() == 1 ||currentWord.charAt(0) != lastWord.charAt(lastWord.length() - 1)) {
                return new int[] {player, turn};
            }
            
            // Add current word to the set and update lastWord
            seenWords.add(currentWord);
            lastWord = currentWord;
        }
        
        // If no errors, return [0, 0] to indicate no failures
        return new int[] {0, 0};
    }
}