134. Gas Station

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There are n gas stations on a circular road. Station i gives you gas[i] units of fuel, and driving from station i to station i + 1 (the last one leads back to station 0) uses cost[i] units. Your tank starts empty and has no limit. Return the index of the station where you can start and drive the full loop once, or -1 if no start works. When an answer exists it is unique.

Example

gas = [1,2,3,4,5], cost = [3,4,5,1,2]  ->  3
gas = [2,3,4], cost = [3,4,3]          ->  -1

Constraints