134. Gas Station

class Solution {
    public int canCompleteCircuit(int[] gas, int[] cost) {
        int totalRemainingGas = 0, remainingGas = 0, startIndex = 0;
        for (int i = 0; i < gas.length; i++) {
            totalRemainingGas += gas[i] - cost[i];
            remainingGas += gas[i] - cost[i];
            if (remainingGas < 0) {
                // 无法到达下一个加油站，只能从下一个加油站开始枚举
                remainingGas = 0;
                startIndex = (i + 1) % gas.length;
            }
        }

        return totalRemainingGas < 0 ? -1 : startIndex;
    }
}

Reference

134. Gas Station
Java 1ms 详细说明起始点选取过程