【leetcode】134. Gas Station【java】

最新推荐文章于 2025-03-19 21:08:28 发布

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本文探讨了一种特定的算法问题——环路加油站问题。该问题要求找到一条从某个加油站出发可以绕环路一周的路径。文章提供了一个Java实现的解决方案，并详细解释了背后的逻辑：当总油量大于总消耗时必定存在可行解。

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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.

public class Solution {
    public int canCompleteCircuit(int[] gas, int[] cost) {
        int sumGas = 0;
        int sumCost = 0;
        int tank = 0;
        int start = 0;
        for (int i = 0; i < gas.length; i++) {
            sumGas += gas[i];
            sumCost += cost[i];
            tank += gas[i] - cost[i];
            if (tank < 0) {
                start = i + 1;
                tank = 0;
            }
        }
        if (sumGas < sumCost) {
            return -1;
        } else {
            return start;
        }
    }
}

The reason why I think this works:
1, if sum of gas is more than sum of cost, then there must be a solution. And the question guaranteed that the solution is unique(The first one I found is the right one).
2, The tank should never be negative, so restart whenever there is a negative number.