Missing Number

You have 1 to N-1 array and 1 to N numbers in it, and one number is missing, you need to find the missing number

Solution:

Solution is simple.We knew that there is a number missing from the array say K .Let S be the sum of the elements of the array.
and S=N*(N+1)/2 – K.

Now we get K=N*(N+1)/2 -S

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