dsa · medium

Gas Station

There are n stations in a circle. gas[i] is the fuel at station i, cost[i] is the fuel to go from i to i+1 (and from n-1 back to 0).

Arguments

• gas — fuel available at each station
• cost — fuel to drive from this station to the next (circular)

Start with an empty tank. Return the starting station index from which you can travel the full circle once, or -1 if impossible. If 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

n == gas.length == cost.length 1 <= n <= 10^5 0 <= gas[i], cost[i] <= 10^4 Hidden tests include near-max size for this bound; a slower-than-intended solution TLEs.

Examples

Example 1

Input:
[1,2,3,4,5]
[3,4,5,1,2]

Expected:
3

Example 2

Input:
[2,3,4]
[3,4,3]

Expected:
-1

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