Check if the Sentence Is Pangram - Practice Coding Problems

Check if the Sentence Is Pangram - Problem

A pangram is a sentence where every letter of the English alphabet appears at least once.

Given a string sentence containing only lowercase English letters, return true if sentence is a pangram, or false otherwise.

Input & Output

Example 1 — Complete Pangram

$ Input: sentence = "thequickbrownfoxjumpsoverthelazydog"

› Output: true

💡 Note: This famous sentence contains every letter from a-z at least once, making it a pangram.

Example 2 — Missing Letters

$ Input: sentence = "leetcode"

› Output: false

💡 Note: Missing many letters like 'a', 'b', 'f', 'g', etc. Only contains: l, e, t, c, o, d (6 unique letters).

Example 3 — Short Sentence

$ Input: sentence = "abc"

› Output: false

💡 Note: Only contains 3 letters (a, b, c) out of the required 26 letters.

Constraints

1 ≤ sentence.length ≤ 1000
sentence consists of lowercase English letters only

Visualization

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Understanding the Visualization

Input

String containing only lowercase letters

Process

Check if all 26 letters a-z appear at least once

Output

Return true if pangram, false otherwise

Key Takeaway

🎯 Key Insight: Use a hash set to track unique letters and return early when all 26 are found

Asked in

G Google 15 a Amazon 12 M Microsoft 8

The key insight is to track unique letters efficiently. Best approach uses a hash set with early termination - add each character to the set and return true immediately when size reaches 26. Time: O(n), Space: O(1).

Common Approaches

Approach	Time	Space	Notes
✓ Brute Force - Check Each Letter	O(26n)	O(1)	For each letter a-z, scan the entire sentence to see if it exists
Frequency Count with Array	O(n)	O(1)	Count frequency of each letter using an array, then check if all 26 positions are non-zero
Hash Set - Optimal Solution	O(n)	O(1)	Use a hash set to track unique letters seen, return true when set size reaches 26

Brute Force - Check Each Letter — Algorithm Steps

Step 1: Loop through each letter from 'a' to 'z'
Step 2: For each letter, scan the entire sentence
Step 3: If any letter is missing, return false
Step 4: If all letters found, return true

Visualization

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Step-by-Step Walkthrough

Check 'a'

Scan entire sentence for letter 'a'

Check 'b'

Scan entire sentence for letter 'b'

Continue

Repeat for all 26 letters

Code -

solution.c — C

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

bool solution(char* sentence) {
    int len = strlen(sentence);
    // Check each letter a-z
    for (int i = 0; i < 26; i++) {
        char letter = 'a' + i;
        bool found = false;
        for (int j = 0; j < len; j++) {
            if (sentence[j] == letter) {
                found = true;
                break;
            }
        }
        if (!found) {
            return false;
        }
    }
    return true;
}

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

Time & Space Complexity

Time Complexity

⏱️

O(26n)

For each of 26 letters, we scan the sentence of length n

✓ Linear Growth

Space Complexity

O(1)

Only using a few variables, no extra data structures

✓ Linear Space

54.5K Views

Medium Frequency

~8 min Avg. Time

2.2K Likes

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Smart Actions

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Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Brute Force - Check Each Letter — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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