LeetCode134——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.

难度系数：

中等

实现

int canCompleteCircuit(vector<int> &gas, vector<int> &cost) {
    int start = gas.size() -1;
    int end = 0;
    int sum = gas[start] - cost[start];
    while (start > end) {
        if (sum >= 0) {
            sum += gas[end] - cost[end];
            end++;
        } else {
            start--;
            sum += gas[start] - cost[start];
        }
    }
    return sum >= 0 ? start : -1;
}