Description:
The sentence 'A quick brown fox jumps over the lazy dog' contains every single letter in the alphabet. Such sentences are called pangrams. You are to write a program, which takes a sentence, and returns all the letters it is missing (which prevent it from being a pangram). You should ignore the case of the letters in sentence, and your return should be all lower case letters, in alphabetical order. You should also ignore all non US-ASCII characters.In case the input sentence is already a pangram, print out the string NULL
Input sample:
Your program should accept as its first argument a filename. This file will contain several text strings, one per line. Ignore all empty lines. eg.
A quick brown fox jumps over the lazy dog
A slow yellow fox crawls under the proactive dog
How razorback jumping frogs can level six piqued gymnasts
Output sample:
Print out all the letters each string is missing in lowercase, alphabetical order .e.g.
NULL
bjkmqz
abcdefghijklmnopqrstuvwxyz
NULL