Check if the Sentence Is Pangram
Easy · Arrays & Hashing · Hash Table · String
Problem
A pangram is a sentence in which every letter of the English alphabet appears at least once.
You are given a string sentence made only of lowercase English letters. Return true if sentence is a pangram, and false otherwise.
Examples
Input: sentence = "sphinxofblackquartzjudgemyvow" Output: true
All 26 letters appear at least once.
Input: sentence = "abcdefghijklmnopqrstuvwxy" Output: false
Every letter but 'z' appears, and one missing letter is enough to fail.
Input: sentence = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" Output: false
Thirty characters, but only one distinct letter. Length alone proves nothing.
Constraints
- 1 <= len(sentence) <= 1000
- sentence consists of lowercase English letters
Approaches
- Set of the letters seen — time O(n), space O(1) (at most 26 entries)
Follow-up
What if the sentence were a stream too large to hold, and you wanted to stop reading as soon as the answer is known? Keep the mask and a count of distinct letters, and stop the moment the count reaches 26. For mixed-case text with spaces and punctuation, lowercase each character and skip anything that is not a letter.
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