[Leetcode]Gas Station

最新推荐文章于 2024-10-12 23:30:39 发布

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本文探讨了一个经典的算法问题——环路加油站问题。该问题要求找到一个起点，使得从该起点出发，可以在消耗一定燃油的情况下绕环路一周并返回起点。文章提供了一种有效的解决方案，并附带了Python实现代码。

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.

Note:

The solution is guaranteed to be unique.

具体分析可以参考 http://blog.youkuaiyun.com/linhuanmars/article/details/22706553

class Solution:
    # @param gas, a list of integers
    # @param cost, a list of integers
    # @return an integer
    def canCompleteCircuit(self, gas, cost):
        if gas is None or len(gas) == 0 or cost is None or len(cost) == 0 or len(gas) != len(cost):
            return -1
        sumVal = total = 0; index = -1
        for i in xrange(len(gas)):
            sumVal += gas[i] - cost[i]
            total += gas[i] - cost[i]
            if sumVal < 0:
                sumVal = 0
                index = i
        return index + 1 if total >= 0 else -1