leetcode :Gas Station

最新推荐文章于 2021-02-13 03:33:59 发布

原创最新推荐文章于 2021-02-13 03:33:59 发布 · 686 阅读

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本文探讨了一个在环形油站路线中寻找起始加油站的问题，以完成一圈行程。通过使用一种特定的算法，可以确定起始加油站的位置，从而实现全程行驶。文章详细解释了算法的实现步骤，并提供了代码示例。

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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.

Note:
The solution is guaranteed to be unique.

class Solution {
public:
    int canCompleteCircuit(vector<int> &gas, vector<int> &cost) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        vector<int> merge;
        int curGas       = 0;
        int curPos       = 0;
        int beginPos     = 0;
        int lenRound     = gas.size();
        
        for (int i=0; i<lenRound; i++)
        {
            merge.push_back(gas[i]-cost[i]);
        }

        curGas = 0;
        curPos = 0;
        
        for (int beginPos=0; beginPos<lenRound;)
        {
            while (curGas>=0 && curPos<beginPos+lenRound)
            {
                curGas += merge[(curPos++)%lenRound];
            }
            
            if (curGas>=0 && curPos==beginPos+lenRound)
            {
                return beginPos;
            }
            
            curGas -= merge[beginPos];
            beginPos++;
        }

        return -1;
    }
};