leetcode 134. Gas Station

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本文探讨了一道经典的算法问题——环路加油站问题。该问题要求找到一条环形路径上能够完成一圈旅行的起点加油站。通过一次遍历算法，确定是否能从某个起点完成整个环路的行驶，并给出实现代码。

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134. Gas Station

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.

思路就是一次遍历，

如果一段路的remain < 0 就说明如果能走完，那么开始的位置肯定不是在当前i的前面，而是在后面。所以start = i + 1

最后的remain+debt能判断能不能走完。

class Solution {
public:
    int canCompleteCircuit(vector<int>& gas, vector<int>& cost) 
    {
       int start = 0;
       int debt = 0;
       int remain = 0;
       
       for (int i = 0; i < gas.size(); i++)
       {
           remain += gas[i]-cost[i];
           if (remain < 0)
           {
               debt += remain;
               start = i+1;
               remain = 0;
           }
       }
       return (remain + debt >= 0) ? start : -1;
    }
};