Detect Capital - Practice Coding Problems

Detect Capital - Problem

String Easy

Detect Capital - String Pattern Recognition

You're a text editor developer implementing a smart capitalization checker! Your task is to determine if a word follows proper capitalization rules.

Valid Capitalization Patterns:
🔹 All uppercase: "USA", "NASA"
🔹 All lowercase: "hello", "world"
🔹 Title case: "Google", "Apple"

Goal: Return true if the word follows one of these patterns, false otherwise.

Think of it like a grammar checker that validates proper noun formatting!

Input & Output

example_1.py — All Uppercase

$ Input: word = "USA"

› Output: true

💡 Note: All letters are uppercase, which is one of the valid capitalization patterns.

example_2.py — Title Case

$ Input: word = "Google"

› Output: true

💡 Note: Only the first letter is uppercase and the rest are lowercase, forming valid title case.

example_3.py — Invalid Mixed Case

$ Input: word = "FlaG"

› Output: false

💡 Note: Mixed capitalization that doesn't follow any valid pattern - not all uppercase, not all lowercase, and not title case.

Visualization

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Understanding the Visualization

Count the Uniforms

Count how many team members are wearing formal uniforms (uppercase letters)

Check the Captain

See if the team captain (first letter) is wearing a formal uniform

Determine Team Status

Valid teams: all formal, all casual, or captain formal with casual team

Key Takeaway

🎯 Key Insight: Only three valid patterns exist, and counting uppercase letters with first letter check covers all cases efficiently in O(n) time.

Time & Space Complexity

Time Complexity

⏱️

O(n)

Single pass through the string of length n

✓ Linear Growth

Space Complexity

O(1)

Only using constant extra space for counter and variables

✓ Linear Space

Constraints

1 ≤ word.length ≤ 100
word consists of lowercase and uppercase English letters only
No empty strings or special characters

Asked in

G Google 25 a Amazon 20 ⊞ Microsoft 15 Apple 10

The optimal approach uses a single pass to count uppercase letters. With just the count and first letter's case, we can determine if the word follows any valid pattern: all uppercase (count = length), all lowercase (count = 0), or title case (count = 1 and first letter uppercase). Time: O(n), Space: O(1).

Common Approaches

Approach	Time	Space	Notes
✓ One-Pass Pattern Detection (Optimal)	O(n)	O(1)	Count uppercase letters in single pass to determine pattern
Multiple Pattern Checks	O(3n) = O(n)	O(1)	Check each valid pattern separately with multiple passes

One-Pass Pattern Detection (Optimal) — Algorithm Steps

Initialize counter for uppercase letters
Iterate through the word once, counting uppercase letters
Check the first letter's case
Use count and first letter case to determine validity

Visualization

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Step-by-Step Walkthrough

Count Uppercase

Single pass counting uppercase letters

Analyze Pattern

Use count and first letter to determine validity

Code -

solution.c — C

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdbool.h>

bool detectCapitalUse(char* word) {
    int len = strlen(word);
    int uppercaseCount = 0;
    
    for (int i = 0; i < len; i++) {
        if (isupper(word[i])) {
            uppercaseCount++;
        }
    }
    
    // Valid patterns:
    // 1. All uppercase: count == len
    // 2. All lowercase: count == 0
    // 3. Title case: count == 1 and first letter is uppercase
    return uppercaseCount == len || 
           uppercaseCount == 0 || 
           (uppercaseCount == 1 && isupper(word[0]));
}

int main() {
    char word[1000];
    fgets(word, sizeof(word), stdin);
    // Remove newline and quotes
    word[strcspn(word, "\n")] = 0;
    if (word[0] == '"') {
        memmove(word, word+1, strlen(word));
        word[strlen(word)-1] = 0;
    }
    printf("%s\n", detectCapitalUse(word) ? "true" : "false");
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n)

Single pass through the string of length n

✓ Linear Growth

Space Complexity

O(1)

Only using constant extra space for counter and variables

✓ Linear Space

Constraints

1 ≤ word.length ≤ 100
word consists of lowercase and uppercase English letters only
No empty strings or special characters

28.5K Views

Medium Frequency

~8 min Avg. Time

890 Likes

Ln 1, Col 1

Smart Actions

💡 Explanation

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// Output will appear here after running code

Code Editor Closed

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Input & Output

Visualization

Time & Space Complexity

Related Problems

Constraints

Common Approaches

One-Pass Pattern Detection (Optimal) — Algorithm Steps

Visualization

Code -

Time & Space Complexity

Constraints

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