There are n gas stations along a circular route, where the amount of gas at the i-th station is gas[i].
You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from the i-th station to the next (i + 1)-th station. You begin the journey with an empty tank at one of the gas stations.
Given two integer arrays gas and cost, return the starting gas station's index if you can travel around the circuit once in the clockwise direction, otherwise return -1. If there exists a solution, it is guaranteed to be unique.
Example 1:
Input: gas = [1,2,3,4,5], cost = [3,4,5,1,2]
Output: 3
Explanation: Start at station 3 (index 3) and fill up with 4 units of gas. Tank = 0 + 4 = 4. Travel to station 4. Tank = 4 - 1 + 5 = 8. Travel to station 0. Tank = 8 - 2 + 1 = 7. Travel to station 1. Tank = 7 - 3 + 2 = 6. Travel to station 2. Tank = 6 - 4 + 3 = 5. Travel to station 3. Tank = 5 - 5 = 0. You can complete the circuit starting from index 3.
Example 2:
Input: gas = [2,3,4], cost = [3,4,3]
Output: -1
Explanation: No matter which station you start at, you cannot complete the circuit. Total gas = 9, total cost = 10, so it is impossible.
Example 3:
Input: gas = [5,1,2,3,4], cost = [4,4,1,5,1]
Output: 4
Explanation: Start at station 4. Tank = 0 + 4 = 4. Travel to station 0. Tank = 4 - 1 + 5 = 8. Travel to station 1. Tank = 8 - 4 + 1 = 5. Travel to station 2. Tank = 5 - 4 + 2 = 3. Travel to station 3. Tank = 3 - 1 + 3 = 5. Travel to station 4. Tank = 5 - 5 = 0. You can complete the circuit starting from index 4.
n == gas.length == cost.length1 <= n <= 10^50 <= gas[i], cost[i] <= 10^4