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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.

class Solution {public:    int canCompleteCircuit(vector<int> &gas, vector<int> &cost) {        int len = gas.size();        int ind = 0;        int remain = 0;        int hold = 0;        bool flag = false;        for(int i=0;i<len;i++){            int r = gas[i]-cost[i];            remain += r;            if(flag == false && r > 0){                ind = i;                flag = true;                hold = hold + remain;                remain = 0;            }            if(remain < 0) flag = false;        }        if(hold + remain >= 0) return ind;        else return -1;    }};

 

Gas Station