leetcode 134. Gas Station

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;    }};