What is the time complexity of Minimum Time to Type Word Using Special Typewriter?

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

What data structures are used to solve Minimum Time to Type Word Using Special Typewriter?

This problem uses String, Greedy. Understanding these concepts is essential for solving this Easy problem efficiently.

What are the key insights for solving Minimum Time to Type Word Using Special Typewriter?

Insight 1: The shortest distance between two characters on a circle can be calculated as the minimum of the clockwise distance and the counterclockwise distance. Insight 2: A greedy approach works optimally. We only need to consider the minimum time to reach each character from the previous character, and we don't need to optimize across multiple characters simultaneously.

Which companies ask LeetCode 1974. Minimum Time to Type Word Using Special Typewriter in interviews?

This problem is frequently asked at LinkedIn, Thomson Reuters.

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Minimum Time to Type Word Using Special Typewriter - LeetCode 1974 Solution

Minimum Time to Type Word Using Special Typewriter - Complete Solution Guide

Minimum Time to Type Word Using Special Typewriter is LeetCode problem 1974, a Easy level challenge. This complete guide provides step-by-step explanations, multiple solution approaches, and optimized code in python3, java, cpp, c.

Problem Statement

There is a special typewriter with lowercase English letters 'a' to 'z' arranged in a circle with a pointer . A character can only be typed if the pointer is pointing to that character. The pointer is initially pointing to the character 'a' . Each second, you may perform one of the following operations: Move the pointer one character counterclockwise or clockwise . Type the character the pointer is currently on. Given a string word , return the minimum number of seconds to type out the character

Detailed Explanation

The problem describes a special typewriter where characters are arranged in a circle. The pointer starts at 'a'. To type a word, you can move the pointer clockwise or counterclockwise, and then type the character the pointer is on. Each move and each type takes one second. The goal is to find the minimum time to type a given word.

Solution Approach

The solution uses a greedy approach. It iterates through each character in the input word. For each character, it calculates the shortest distance to that character from the current pointer position. The distance is calculated using the absolute difference between their ASCII values and taking the minimum of this difference and its complement (26 - difference) to account for the circular arrangement. Then, it adds 1 (for typing the character) to the total time and updates the pointer position to the current character.

Step-by-Step Algorithm

Step 1: Initialize `current` character to 'a' and `total_time` to 0.
Step 2: Iterate through each character `char` in the input `word`.
Step 3: Calculate the absolute difference `diff` between the ASCII values of `char` and `current`.
Step 4: Calculate the minimum time to move the pointer: `min(diff, 26 - diff)`.
Step 5: Add the minimum move time and 1 (for typing) to `total_time`.
Step 6: Update `current` to `char`.
Step 7: After iterating through all characters, return `total_time`.

Key Insights

Insight 1: The shortest distance between two characters on a circle can be calculated as the minimum of the clockwise distance and the counterclockwise distance.
Insight 2: A greedy approach works optimally. We only need to consider the minimum time to reach each character from the previous character, and we don't need to optimize across multiple characters simultaneously.
Insight 3: Using ASCII values and the `abs()` function simplifies the distance calculation between characters.

Complexity Analysis

Time Complexity: O(n)

Space Complexity: O(1)

Topics

This problem involves: String, Greedy.

Companies

Asked at: LinkedIn, Thomson Reuters.

Minimum Time to Type Word Using Special Typewriter | LeetCode 1974

Easy

String Greedy

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

Solution Code

Available in:

class Solution {
    public int minTimeToType(String word) {
        int time = 0;
        char current = 'a';
        for (char c : word.toCharArray()) {
            int diff = Math.abs(c - current);
            time += Math.min(diff, 26 - diff) + 1;
            current = c;
        }
        return time;
    }
}

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Problem Info

Description

Problem 1974: Minimum Time to Type Word Using Special Typewriter - Detailed explanation and solution approaches.

Topics

String Greedy

Companies

LinkedInThomson Reuters

Stats

Difficulty:Easy

Languages:4

Companies:2

Problem #:1974

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` character to 'a' and `total_time` to 0.
2
Step 2: Iterate through each character `char` in the input `word`.
3
Step 3: Calculate the absolute difference `diff` between the ASCII values of `char` and `current`.
4
Step 4: Calculate the minimum time to move the pointer: `min(diff, 26 - diff)`.
5
Step 5: Add the minimum move time and 1 (for typing) to `total_time`.
6
Step 6: Update `current` to `char`.
7
Step 7: After iterating through all characters, return `total_time`.

💡

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 time complexity is dominated by the single loop iterating through the input word. The space complexity is constant because we only store a few variables (`current`, `total_time`, `diff`).

📖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 circular array

Represent the alphabet as a circular array. Calculate distances by traversing the array.

Time: O(n)Space: O(26)

Trade-offs: This approach is less concise than using ASCII values but might be easier to understand conceptually for beginners.

✨

Key Insights

1Insight 1: The shortest distance between two characters on a circle can be calculated as the minimum of the clockwise distance and the counterclockwise distance.
2Insight 2: A greedy approach works optimally. We only need to consider the minimum time to reach each character from the previous character, and we don't need to optimize across multiple characters simultaneously.
3Insight 3: Using ASCII values and the `abs()` function simplifies the distance calculation between characters.

📚

Key Terms Explained

For Students

Greedy Algorithm

Making the best choice at each step without looking ahead.

String

A sequence of characters. Like a word or sentence in programming!

Edge Cases

Edge case 1: Empty word. The solution correctly handles this by returning 0.
Edge case 2: Word containing only 'a'. The solution correctly handles this, only adding the time for typing each 'a'.

⚠️

Common Mistakes to Avoid

✗Common mistake 1: Forgetting to add 1 for typing the character in each iteration.

✗Common mistake 2: Incorrectly calculating the minimum distance on the circular arrangement – failing to consider both clockwise and counterclockwise distances.

✅

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: Optimizing robotic arm movements. This problem is analogous to minimizing the time to move a robotic arm to different positions on a circular track.

🏦Real-world scenario 2: Designing efficient algorithms for data entry on circular input devices (e.g., rotary encoders).

💡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

String problems often involve sliding windows or two pointers. Consider if the character set is limited (lowercase letters = only 26 possibilities).

🎯 Interview Tip

Even for easy problems, discuss time and space complexity. Interviewers want to see you think analytically.

⚠️ Watch Out

Mutating strings directly in languages where strings are immutable. Use StringBuilder or arrays.

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: November 22, 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

In a real interview, always clarify constraints first. Ask about input size and value ranges.

@TechLeadJul 13

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

@DevExpert92Jul 6

❓

Frequently Asked Questions

How do I handle string manipulation efficiently?

In languages with immutable strings (Java, Python, C#), use StringBuilder/list to avoid O(n) concatenation cost. Consider using character arrays for in-place modifications. For pattern matching, consider KMP or Rabin-Karp for O(n+m) complexity.

How do I verify if a greedy approach is correct?

Prove the greedy choice property: the locally optimal choice leads to globally optimal solution. Use exchange argument: show that swapping any element with the greedy choice doesn't improve the solution. If you can't prove it, test extensively or consider DP.

How should I approach easy-level algorithm problems?

Easy problems build foundational skills. Focus on: 1) Understanding the problem completely before coding, 2) Writing clean, readable code, 3) Handling all edge cases (empty input, single element, etc.), 4) Analyzing time and space complexity. Don't skip complexity analysis even for simple solutions.

How should I practice algorithm problems effectively?

Focus on understanding patterns rather than memorizing solutions. After solving a problem, review optimal solutions and understand the intuition. Group similar problems to recognize patterns. Practice explaining your approach out loud. Review problems after a few days to test retention.

What is the optimal approach for "Minimum Time to Type Word Using Special Typewriter"?

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

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