What is the time complexity of Find The First Player to win K Games in a Row?

The optimal solution has a time complexity of O(n).

What data structures are used to solve Find The First Player to win K Games in a Row?

This problem uses Array, Simulation. Understanding these concepts is essential for solving this Medium problem efficiently.

What are the key insights for solving Find The First Player to win K Games in a Row?

Insight 1: The player with the highest skill will eventually win since the skills are unique. If k is large enough, this player will always be the answer. Insight 2: It's important to track the current winner and their consecutive wins. If the current player loses, the winner and consecutive win counts must be updated.

Which companies ask LeetCode 3175. Find The First Player to win K Games in a Row in interviews?

This problem is frequently asked at IBM.

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Find The First Player to win K Games in a Row - LeetCode 3175 Solution

Find The First Player to win K Games in a Row - Complete Solution Guide

Find The First Player to win K Games in a Row is LeetCode problem 3175, a Medium level challenge. This complete guide provides step-by-step explanations, multiple solution approaches, and optimized code in python3, java, cpp, c.

Problem Statement

A competition consists of n players numbered from 0 to n - 1 . You are given an integer array skills of size n and a positive integer k , where skills[i] is the skill level of player i . All integers in skills are unique . All players are standing in a queue in order from player 0 to player n - 1 . The competition process is as follows: The first two players in the queue play a game, and the player with the higher skill level wins. After the game, the winner stays at the beginning of the queue,

Detailed Explanation

The problem describes a competition among 'n' players with unique skill levels. Players are initially arranged in a queue. In each round, the first two players in the queue compete, and the player with the higher skill wins. The winner remains at the front of the queue, while the loser goes to the end. The goal is to find the index of the first player who wins 'k' games in a row.

Solution Approach

The solution iterates through the 'skills' array, starting from the second player. It maintains the index of the 'current_winner' and the number of 'consecutive_wins'. In each iteration, it compares the skill of the current winner with the skill of the next player. If the current winner has a higher skill, the 'consecutive_wins' counter is incremented. Otherwise, the next player becomes the new current winner, and the 'consecutive_wins' counter is reset to 1. The loop continues until a player wins 'k' games in a row. If the loop completes without a winner, the player with the highest skill always wins the entire competition because `skills` are unique; thus, we return the current winning index.

Step-by-Step Algorithm

Step 1: Initialize 'current_winner_idx' to 0 (the first player) and 'consecutive_wins' to 0.
Step 2: Iterate through the 'skills' array from index 1 to the end.
Step 3: In each iteration, compare the skill of the player at 'current_winner_idx' with the skill of the player at the current index 'i'.
Step 4: If the 'current_winner_idx' player has a higher skill, increment 'consecutive_wins'.
Step 5: Otherwise, update 'current_winner_idx' to 'i' and reset 'consecutive_wins' to 1.
Step 6: Check if 'consecutive_wins' is equal to 'k'. If it is, return 'current_winner_idx'.
Step 7: If the loop completes without finding a winner, return 'current_winner_idx' (the player that has the highest skill)

Key Insights

Insight 1: The player with the highest skill will eventually win since the skills are unique. If k is large enough, this player will always be the answer.
Insight 2: It's important to track the current winner and their consecutive wins. If the current player loses, the winner and consecutive win counts must be updated.
Insight 3: We don't need to simulate the entire queue rotation. The code only needs to track the current winner and consecutive wins, comparing the winner's skill with the next player in line.

Complexity Analysis

Time Complexity: O(n)

Space Complexity: O(1)

Topics

This problem involves: Array, Simulation.

Companies

Asked at: IBM.

Find The First Player to win K Games in a Row | LeetCode 3175

Medium

Array Simulation

Time: O(n)Space: O(1)

Solution Code

Available in:

class Solution {
    public int findWinningPlayer(int[] skills, int k) {
        int current_winner_idx = 0;
        int consecutive_wins = 0;

        for (int i = 1; i < skills.length; i++) {
            if (skills[current_winner_idx] > skills[i]) {
                consecutive_wins += 1;
            } else {
                current_winner_idx = i;
                consecutive_wins = 1;
            }

            if (consecutive_wins == k) {
                return current_winner_idx;
            }
        }

        return current_winner_idx;
    }
}

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Problem Info

Description

Problem 3175: Find The First Player to win K Games in a Row - Detailed explanation and solution approaches.

Topics

Array Simulation

Companies

IBM

Stats

Difficulty:Medium

Languages:4

Companies:1

Problem #:3175

Problem Explanation

💡

Think Before You Code

🤔 Ask Yourself

→What is the input? What output do I need?
→Can I solve a smaller version of this problem first?
→What patterns have I seen in similar problems?

✏️ Try This First

Before looking at the solution, try to solve it on paper with a simple example!

🚀 Try on LeetCode

Solution Approach

📋

Step-by-Step Solution

7 steps

1
Step 1: Initialize 'current_winner_idx' to 0 (the first player) and 'consecutive_wins' to 0.
2
Step 2: Iterate through the 'skills' array from index 1 to the end.
3
Step 3: In each iteration, compare the skill of the player at 'current_winner_idx' with the skill of the player at the current index 'i'.
4
Step 4: If the 'current_winner_idx' player has a higher skill, increment 'consecutive_wins'.
5
Step 5: Otherwise, update 'current_winner_idx' to 'i' and reset 'consecutive_wins' to 1.
6
Step 6: Check if 'consecutive_wins' is equal to 'k'. If it is, return 'current_winner_idx'.
7
Step 7: If the loop completes without finding a winner, return 'current_winner_idx' (the player that has the highest skill)

💡

Pro Tip for Students

Try tracing through each step with a small example on paper before coding. Understanding "why" each step happens is more important than memorizing the code!

⚡

Complexity Analysis

⏱️

Time Complexity

O(n)

👍 Linear - Good! Visits each element once.

💾

Space Complexity

O(1)

💪 Constant space - Uses same memory regardless of input!

📝

Why?

The algorithm processes each element of the input array 'skills' at most once. Therefore, the time complexity is directly proportional to the size of the input, resulting in O(n) time complexity. Only a fixed number of variables are used regardless of the input size, hence the constant space complexity of O(1).

📖New to Big O? Click to learn more

Big O Notation - Quick Guide

O(1)Best - Instant

O(log n)Excellent - Binary Search

O(n)Good - One loop

O(n log n)OK - Sorting

O(n²)Slow - Nested loops

O(2ⁿ)Very Slow - Recursion

Alternative Approaches

Using a Queue Data Structure

Simulate the queue operations directly using a queue data structure. This approach mimics the problem description more closely.

Time: O(n*k) in the worst case. In the worst-case scenario, the simulation may need to run for n*k games.Space: O(n) to store the queue of players.

Trade-offs: The queue-based approach is conceptually simpler but less efficient than the provided solution. Use it when you need to strictly adhere to the simulation process, even at the cost of performance.

✨

Key Insights

1Insight 1: The player with the highest skill will eventually win since the skills are unique. If k is large enough, this player will always be the answer.
2Insight 2: It's important to track the current winner and their consecutive wins. If the current player loses, the winner and consecutive win counts must be updated.
3Insight 3: We don't need to simulate the entire queue rotation. The code only needs to track the current winner and consecutive wins, comparing the winner's skill with the next player in line.

📚

Key Terms Explained

For Students

Array

A collection of items stored at contiguous memory locations. Like a row of boxes.

Edge Cases

Edge case 1: k = 1. In this case, the first player always wins the first game. The solution correctly handles this because it only checks for the winner when consecutive_wins == k and will return the index of the first winner.
Edge case 2: If k is larger than n - 1, the player with the highest skill will win. The loop finishes and returns the index of the player with the highest skill.
Edge case 3: If skills is an empty array, the code will crash. However, the problem constraints state that n >= 2, therefore this case is not possible.

⚠️

Common Mistakes to Avoid

✗Common mistake 1: Not resetting the consecutive win counter when a new winner emerges.

✗Common mistake 2: Incorrectly tracking the index of the current winner.

✗Common mistake 3: Assuming the winner is always the player with the highest skill without considering the 'k' consecutive wins requirement.

✅

Learning Tip

Every mistake is a learning opportunity! When you make an error, understand why it happened before moving on.

🌍

Where is This Used in Real Life?

💼Real-world scenario 1: Determining the winner of a series of tournaments where a team needs to win a certain number of consecutive matches to be declared the champion.

🏦Real-world scenario 2: Modeling a system where resources are allocated based on consecutive successful operations. If a process performs 'k' successful operations consecutively, it gains priority or access to more resources.

💡Understanding real-world applications helps you see the "why" behind algorithms. It's not just about passing interviews—these concepts power the apps and websites you use every day!

Author's Notes

💡 Key Insight

When dealing with arrays, always consider if sorting would simplify the problem. Many array problems have O(n) solutions using hash maps or two-pointer technique.

🎯 Interview Tip

If stuck, try working through a small example by hand. The pattern often reveals itself.

⚠️ Watch Out

Off-by-one errors are the most common mistake. Double-check your loop bounds and array indices.

👨‍💻 From Experience

This problem pattern appears frequently in real codebases. I've used similar logic when building production systems.

Written by Saswata Mondal

Software Engineer • Algorithms Enthusiast • Interview Coach

👨‍💻

About the Author

👨‍💻

Saswata MondalAuthor400+ LC Problems

B.Tech CSE, IEM Kolkata | LeetCode Rating: 1672 (Top 15%)

Certified: IBM Java Developer, NPTEL Programming in Java

Last updated: September 24, 2024LeetCode Profile GitHub

This solution has been crafted based on my experience solving 400+ LeetCode problems. Each explanation is designed to help you understand the underlying concepts, not just memorize the code.

Community Tips & Insights

Don't forget to handle the edge case when the input is empty. Many candidates miss this in interviews.

@DevExpert92Jul 13

The key insight here is recognizing the pattern. Once you see it, the solution becomes straightforward.

@AlgoMasterJul 6

I was asked this exact problem at my Google interview. The interviewer wanted me to optimize space complexity.

@InterviewProJun 29

❓

Frequently Asked Questions

When should I use in-place modification vs creating a new array?

Use in-place modification when space complexity matters (O(1) space requirement) and the original array can be modified. Create a new array when you need to preserve the original data or when the problem involves significant restructuring that would complicate in-place logic.

How much time should I spend on a medium problem in interviews?

In a 45-minute interview, aim for: 5-10 minutes understanding and clarifying, 5-10 minutes discussing approach, 20-25 minutes coding, and 5-10 minutes testing. If stuck after 15 minutes of thinking, verbalize your thought process and ask for hints.

What is the importance of time and space complexity analysis?

Complexity analysis is crucial because: 1) Interviewers always ask about it, 2) It helps you choose between approaches, 3) It demonstrates CS fundamentals. Always state both time and space complexity, and be prepared to explain how you derived them.

What is the optimal approach for "Find The First Player to win K Games in a Row"?

For this medium-level Array problem, the key is to identify the core pattern. Analyze the input constraints to determine acceptable time complexity. Consider whether simulation techniques can optimize the solution. Always handle edge cases and validate your approach with examples before coding.

🤖 Need help with this problem?