Question

Gas Station with Math Proofs | Leetcode 134 - YouTube

Code

• if the current sum is negative, or turned negative, it would be not the start position, since the car cannot move further
• if it is positive, the res still doesn't change, since the answer is unique, and we need to find the one with max difference

class Solution(object):
    def canCompleteCircuit(self, gas, cost):
        if sum(gas) < sum(cost):
            return -1

        curSum = 0
        res = 0
        for i in range(len(gas)):
            curSum += (gas[i] - cost[i])
            
            if curSum < 0:
                res = i + 1
                curSum = 0

        return res