From spec to skeleton

From spec to skeleton. A method that reads like the spec is fast to write and hard to get wrong. Worked example — "second smallest, -1 if it doesn't exist":

// pass 1: find min
// pass 2: find min among values strictly greater than min
// if pass 2 finds nothing: -1

Two passes, each trivially correct, and the -1 falls out of pass 2 naturally. The one-pass version (tracking first and second simultaneously) is twice the branches and the favorite source of off-by-one ties. When the spec has a tie-break, prefer the two-pass form — the tie-break becomes one comparison instead of three.

For recursion tasks, write the two lines first: the base case and the recursive step with its progress. Then everything else is glue.