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.
public int canCompleteCircuit(int[] gas, int[] cost) { if (gas == null) { return -1; } // Note: The Solution object is instantiated only once and is reused by each test case. int count = gas.length; int n = 0; int gasInCar = 0; int begin = 0; int end = 0; int i = 0; while (n < count - 1) { gasInCar += gas[i] - cost[i]; if (gasInCar >=0) {//forward end++; i=end; } else { begin--; if (begin < 0) { begin = count - 1; } i = begin; } n++; } gasInCar += gas[i] - cost[i]; if (gasInCar >= 0) { return begin; } else { return -1; } }
原文：http://www.cnblogs.com/zhhwgis/p/3959973.html