There is a horrifically easy way ofc. Sum the array then subtract from 5050 (the sum of 1 - 100). There is your missing number. EDIT: I didnt read the reddit

There is a horrifically easy way ofc. Sum the array then subtract from 5050 (the sum of 1 - 100). There is your missing number. EDIT: I didnt read the reddit thread before posting this... why would you say that is the wrong approach? (or, bleh. your being ironic.. sorry ;) too early in the morning).