LeetCode – Refresh – Gas Station

Not quite hard. Just remember initialize index to 0. Because if you initialize it as -1 and all the gas satisfy the cost, it will return -1.

Actually, it was 0.

 

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