134 - Gas Station
Written on October 21, 2015
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There are N gas stations along a circular route, where the amount of gas at station i is gas[i]. You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station i to its next station (i+1). You begin the journey with an empty tank at one of the gas stations. Return the starting gas station’s index if you can travel around the circuit once, otherwise return -1.
class Solution(object):
def canCompleteCircuit(self, gas, cost):
"""
:type gas: List[int]
:type cost: List[int]
:rtype: int
"""
if not gas or not cost:
return -1
left_gas = index = 0
for i in range(len(gas)):
left_gas += gas[i] - cost[i]
if left_gas < 0:
left_gas = 0
index = i + 1
return index if sum(gas) >= sum(cost) else -1