Kata

An ordered sequence of numbers from 1 to N is given. One number might have deleted from it, then the remaining numbers were mixed. Find the number that was deleted.

Example:

• The starting array sequence is [1,2,3,4,5,6,7,8,9]
• The mixed array with one deleted number is [3,2,4,6,7,8,1,9]
• Your function should return the int 5.

If no number was deleted from the starting array, your function should return the int 0.

Note: N may be 1 or less (in the latter case, the first array will be []).