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) {        // Note: The Solution object is instantiated only once and is reused by each test case.        int total = 0,sum = 0,diff = 0;;        int j = -1;                for(int i = 0;i<gas.size();i++)        {            diff = gas[i]-cost[i];            total += diff;            sum += diff;                        if(sum < 0)            {                j = i;                sum = 0;            }        }                return (total >=0)?j+1:-1;    }};

40 ms