leetcode---gas-station---贪心

最新推荐文章于 2019-09-06 12:13:38 发布

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本文探讨了一种特定的算法问题：给定环路上的加油站及其油量与从一站到下一站所需的油耗，如何找到能够完成环路旅程的起始加油站。通过分析加油站数量、油量与消耗之间的关系，提出了一种有效解决方案。

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There are N gas stations along a circular route, where the amount of gas at station i isgas[i].
You have a car with an unlimited gas tank and it costscost[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) 
    {
        int n = gas.size();
        if(n == 0)
            return 0;

        int gasSum = 0, costSum = 0;
        for(int i=0; i<n; i++)
        {
            gasSum += gas[i];
            costSum += cost[i];
        }
        if(gasSum < costSum)
            return -1;

        int maxDis = -1, id = 0;
        for(int i=0; i<n; i++)
        {
            int tmp = 0;
            tmp += gas[i] - cost[i];
            if(tmp < 0)
                continue;
            for(int j=i+1; j!=i; (++j)%=n)
            {
                tmp += gas[j%n] - cost[j%n];
                if(tmp < 0)
                    break;
            }
            if(tmp > maxDis)
            {
                maxDis = tmp;
                id = i;
            }
        }
        return id;
    }
};