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.

class Solution {public:    int canCompleteCircuit(vector<int>& gas, vector<int>& cost) {        int n = gas.size();        int gasAmount = 0;        int total = 0, minSum = INT_MAX, index = 0;        for(int i = 0; i < n; i ++){            total += gas[i] - cost[i];            if(total < minSum){                minSum = total;                index = i + 1;            }        }        return (total < 0) ? -1 : (index % n) ;    }};