[Leetcode] Gas Station

Gas Station

 

AC Rate: 1017/4717

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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.

similar with max range sum.

 

class Solution {
public:
    int canCompleteCircuit(vector<int> &gas, vector<int> &cost) {
        int n = gas.size();
        vector<int> v(n);
        for (int i = 0; i < n; i++) v[i] = gas[i] - cost[i];
        int s = 0, e = 0, t = 0;
        while (s < n) {
            while (t >= 0 && e < s + n) t += v[(e++) % n];
            if (t >= 0 && e == s + n) return s;
            t -= v[s];
            s++;
        }
        return -1;
    }
};