Given an array of 100 integers where every integer from 1-101 occurs once, except for one. Find the missing integer.

Question

Anonymous · Accepted Answer

Let a = XOR of all elements in array and b = XOR of all numbers from 1 to 100. The final result is a XOR b

Anonymous · Answer

sum of number from 1 to n is n(n+1)/2

So Sum from 1 to 101 = (101*102)/2 = 5151

So missing number is 5151 - (sum of all elements in the given array)

Anonymous · Answer

XOR all numbers in the array + till closest power of 2 - 1(in this case 127). Output will be the missing number.

i.e. 1 ^ 2 ^ 3 ....... ^ 101 ^ 102...... ^ 127 = missing number

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