Gas Station leetcode java

题目：

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.

题解：

网上搜到的解法。

据说是Bloomberg的面试题。

用两个变量存+= gas[i] - cost[i]。一个帮助判断当前这个点作为gas station的起点合不合适，一个帮助判断总的需求是不是大于供给。如果总的需求大于供给那么肯定是无解的，如果需求小于等于供给，就可以返回刚才找到的起始点。

代码如下：

 1     public int canCompleteCircuit(int[] gas, int[] cost) {

 2         if (gas==null|| cost==null||gas.length==0||cost.length==0||gas.length!=cost.length)

 3          return -1;

 4          

 5         int sum = 0;  

 6         int total = 0;  

 7         int index = 0;  

 8         for(int i = 0; i < gas.length; i++){  

 9             sum += gas[i]-cost[i];  

             total += gas[i]-cost[i];  

             if(sum < 0){  

                 index=i+1; 

                 sum = 0;   

             } 

         }  

         if(total<0)

             return -1;  

         else

             return index;  

     }

Reference：http://blog.csdn.net/lbyxiafei/article/details/12183461

巴特西

Gas Station leetcode java

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