Detect Capital - Practice Coding Problems

Detect Capital - Problem

String Easy

We define the usage of capitals in a word to be right when one of the following cases holds:

All letters in this word are capitals, like "USA"
All letters in this word are not capitals, like "leetcode"
Only the first letter in this word is capital, like "Google"

Given a string word, return true if the usage of capitals in it is right.

Input & Output

Example 1 — Proper Case

$ Input: word = "Google"

› Output: true

💡 Note: First letter 'G' is uppercase, remaining letters 'o', 'o', 'g', 'l', 'e' are lowercase. This matches the third valid pattern.

Example 2 — All Uppercase

$ Input: word = "USA"

› Output: true

💡 Note: All letters 'U', 'S', 'A' are uppercase. This matches the first valid pattern.

Example 3 — Invalid Mixed Case

$ Input: word = "FlaG"

› Output: false

💡 Note: Mixed case with 'F' and 'G' uppercase, 'l' and 'a' lowercase. This doesn't match any of the three valid patterns.

Constraints

1 ≤ word.length ≤ 100
word consists of lowercase and uppercase English letters

Visualization

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Understanding the Visualization

Input Word

Check capitalization pattern of input string

Pattern Match

Verify against three valid patterns

Result

Return true if matches any valid pattern

Key Takeaway

🎯 Key Insight: Only three patterns are valid - count uppercase letters to efficiently determine which pattern matches

Asked in

G Google 15 M Microsoft 12

The key insight is that there are only three valid capitalization patterns. The optimal approach counts uppercase letters in a single pass: if count is 0 (all lower), equals length (all upper), or equals 1 with first letter uppercase (proper case), return true. Time: O(n), Space: O(1)

Common Approaches

Approach	Time	Space	Notes
✓ Single Pass Count	O(n)	O(1)	Count uppercase letters in one pass and determine pattern
Pattern Checking	O(n)	O(1)	Check if word matches any of the three valid patterns

Single Pass Count — Algorithm Steps

Count uppercase letters in single pass
Check if count equals 0 (all lower), length (all upper), or 1 with first upper

Visualization

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Step-by-Step Walkthrough

Count Uppers

Count uppercase letters in one pass

Check Patterns

Compare count against valid patterns

Determine Result

Return true if matches any pattern

Code -

solution.c — C

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

bool solution(char* word) {
    int len = strlen(word);
    if (len == 0) return true;
    
    int upperCount = 0;
    for (int i = 0; i < len; i++) {
        if (isupper(word[i])) {
            upperCount++;
        }
    }
    
    // All lowercase
    if (upperCount == 0) return true;
    // All uppercase
    if (upperCount == len) return true;
    // Only first is uppercase
    if (upperCount == 1 && isupper(word[0])) return true;
    
    return false;
}

int main() {
    char word[1000];
    fgets(word, sizeof(word), stdin);
    word[strcspn(word, "\n")] = 0;
    bool result = solution(word);
    printf(result ? "true\n" : "false\n");
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n)

Single pass through the string to count uppercase letters

✓ Linear Growth

Space Complexity

O(1)

Only using integer counter and boolean variables

✓ Linear Space

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Medium Frequency

~15 min Avg. Time

890 Likes

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Smart Actions

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Input & Output

Constraints

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Related Problems

Common Approaches

Single Pass Count — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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