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  1. /**
  2.  * Question:
  3.  * Write a method that takes an array of consecutive (increasing) letters as
  4.  * input and that returns the missing letter in the array.
  5.  * 
  6.  * Input Constrains:
  7.  * You will always get a valid array. And it will be always exactly one letter
  8.  * be missing. The length of the array will always be at least 2.
  9.  * The array will always contain letters in only one case.
  10.  */
  11. function findMissingLetter(arr) {
  12. 	// Base condition
  13. 	// When array length is less than 2 then the second letter is missing.
  14. 	if (arr.length <= 2) {
  15. 		return String.fromCharCode(arr[0].charCodeAt(0) + 1);
  16. 	}
  17.  
  18. 	const midPos1 = Math.floor((arr.length-1)/2);
  19. 	const midPos2 = Math.floor(arr.length/2);
  20. 	const start = arr[0].charCodeAt(0);
  21. 	const mid1 = arr[midPos1].charCodeAt(0);
  22. 	const mid2 = arr[midPos2].charCodeAt(0);
  23. 	const end = arr[arr.length - 1].charCodeAt(0);
  24.  
  25. 	if (mid1 - start > end - mid2) {
  26. 		return findMissingLetter(arr.slice(0, midPos1));
  27. 	} else if (mid1 - start < end - mid2) {
  28. 		return findMissingLetter(arr.slice(midPos2));
  29. 	} else {
  30. 		// If both split are equal then the letter missing is at the center.
  31. 		return String.fromCharCode(mid1 + 1);
  32. 	}
  33. }
  34.  
  35. while ((str = readline())) {
  36. 	console.log(findMissingLetter(str.split('')));
  37. }
Success #stdin #stdout 0.02s 16916KB
comments (?)
stdin
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abcdf
acdef
OQRS
OPRS
stdout
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e
b
P
Q
https://ideone.com/YXz3HL
language:
JavaScript (SMonkey 60.2.3)
created:
4 years ago
visibility:
public

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