Gas Station

最新推荐文章于 2024-10-12 23:30:39 发布

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本文介绍了一个算法问题：如何确定能否从某加油站出发绕环路一周。通过模拟判断每个加油站作为起点的可能性，排除不可行的起点，最终找到合适的出发点。

Gas Station

There are N gas stations along a circular route, where the amount of gas at stationi is gas[i].

You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from stationi 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.

public int canCompleteCircuit(int[] gas, int[] cost) {
        int loc[] = new int[gas.length];
        int i = 0, j = 0, rem = 0, count=0;
        while (count < gas.length && j<gas.length) {
            if (loc[j] == gas.length) return j;
            if (rem + gas[i] >= cost[i]) {
                rem += (gas[i] - cost[i]);
                loc[j]++;
            } else {
                rem = 0;
                j = i+1;
                count++;
            }
            i=(i+1)%gas.length;
        }
        return -1;
    }

考虑1号加油站，直接模拟判断它是否为解。如果是，直接输出；如果不是，说明在模拟的过程中遇到了某个加油站p，在从它开到加油站p+1时油没了。这样，以2, 3,…, p为起点也一定不是解。这样，使用简单的枚举法便解决了问题，时间复杂度为O(n)