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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.
Solution:
1 public class Solution { 2 public int canCompleteCircuit(int[] gas, int[] cost) { 3 if (gas.length==0) return -1; 4 if (gas.length==1) 5 if (gas[0]-cost[0]>=0) return 0; 6 else return -1; 7 8 int len = gas.length; 9 int left = 0; 10 int index = 0; 11 while (index<len){ 12 left = 0; 13 //Check whether the current station is the solution. 14 boolean valid = true; 15 int p = index; 16 while (p!=(index+gas.length-1)%gas.length){ 17 if (left+gas[p]-cost[p]<0){ 18 valid = false; 19 break; 20 } else{ 21 left += gas[p]-cost[p]; 22 p = (p+1)%gas.length; 23 } 24 } 25 if (valid && left+gas[p]-cost[p]>=0) return index; 26 else if ((p+1)%gas.length<=index) return -1; 27 else index = p+1; 28 } 29 30 return -1; 31 } 32 }
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原文地址：http://www.cnblogs.com/lishiblog/p/4179301.html
