LeetCode：Gas Station

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.

int canCompleteCircuit(vector<int> &gas, vector<int> &cost) {
if(gas.size()!=cost.size())
return -1;
if(gas.empty())
return -1;
int total = 0;
int start = 0;
int sum = 0;
for(int i = 0;i<gas.size();i++)
{
total += gas[i] - cost[i];
sum += gas[i] - cost[i];
if(sum<0)
{
start = i+1;
sum = 0;
}
}
return total >= 0 ? start : -1;
}

已AC 40ms