Programming Problem: Pangram

Article #9 in a 9-part series.

1 - Programming Problem: Determine if Two Strings Are Anagrams
2 - Programming Problem: Sum-Zero Triplet
3 - Programming Problem: Palindromes
4 - Problem: Validate a Phone Number
5 - Programming Problem: Single-Edit Difference
6 - Prime Factors Problem 1: LCM
7 - Prime Factors Problem 2: Largest Prime Factor
8 - How-To: Substrings in Swift
9 - this article

Goal: write a method to determine if a string is a pangram.

observations

A pangram is a phrase using all the letters of the alphabet.

The quick brown fox jumps over the lazy dog.
The five boxing wizards jump quickly.
Bright vixens jump; dozy fowl quack.

assumptions

For this problem let the alphabet consist of only letters ignoring case, and let’s assume our input may include punctuation, digits, or spaces.

program

Give it a try in your programming language of choice, and try to be brief. Test negative case by removing words from the pangram. Below I share my solutions in Swift and C#.

my solution examples

A pangram uses all letter characters at least once. Counting would be one option, but notice we’re looking for a phrase that is the superset of the alphabet.

Swift 3

Turn the phrase into a Set and find if the phrase-set is a superset of the letters-set.

Swift 5: is the string a pangram?

//: Playground - noun: a place where people can play
 
import Cocoa
 
let letters = "abcdefghijklmnopqrstuvwxyz"
let phrase = "The quick brown fox jumps over Lazy Dog."
let phraseFail = "The brown fox jumps over the lazy dog."
let letterSet = Set(letters)
let phraseSet = Set(phrase.lowercased()
let phraseFailSet = Set(phraseFail.lowercased()
 
if phraseSet.isSuperset(of: letterSet) {
    print("is pangram")
}
else {
    print("Not pangram")
}
if phraseFailSet.isSuperset(of: letterSet) {
    print("is pangram")
}
else {
    print("Not pangram")
}

For this solution I used LINQ to query distinct letters which should equal the length of our English alphabet, 26. Learn more about LINQ on MSDN.

C#: is the string a pangram?

using System;
using System.Linq;
 
namespace MyTutorialConsoleApp
{
    public static class StringPlay
    {
        public static bool IsPangram(string phrase)
        {
            if (String.IsNullOrWhiteSpace(phrase) || phrase.Length < 26)
            {
                return false;
            }
 
            if (phrase.Where(char.IsLetter).Select(char.ToLower).Distinct().Count() == 26)
            {
                return true;
            }
 
            return false;
        }
    }
}

Article #9 in a 9-part series.

1 - Programming Problem: Determine if Two Strings Are Anagrams
2 - Programming Problem: Sum-Zero Triplet
3 - Programming Problem: Palindromes
4 - Problem: Validate a Phone Number
5 - Programming Problem: Single-Edit Difference
6 - Prime Factors Problem 1: LCM
7 - Prime Factors Problem 2: Largest Prime Factor
8 - How-To: Substrings in Swift
9 - this article