Practice: Linear Search

Eleven problems for the one-pass search. Each is the lesson's loop with a different test or a different thing remembered. Decide before you type: first match or last? stop at the match, or keep going? what if there is none?

• The Final Log Entry: the last occurrence — no break.
• The Breaking Point and First Above Threshold: the first element strictly above k.
• Twin Signals: the first i with a[i] == a[i + 1]; the loop stops one short of the end.
• First Local Peak: a test that looks at both neighbours, so i runs from 1 to n − 2.
• The Closest Match and Closest Value: keep the best so far and its index; a strict < keeps the first of equals. Closest Value prefers the smaller value on a tie — compare the pair {distance, value} — and its numbers reach 10¹⁸.
• First Occurrence and Last Occurrence: 5·10⁶ numbers; keep the fast-IO lines and read into a vector<int>.
• In Subarray: the search runs from l to r (1-indexed in the statement).
• Matrix Position: a search over a grid, row by row, stopping at the first hit — break out of both loops, or return from a function.