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.
class Solution { public: int canCompleteCircuit(vector<int> &gas, vector<int> &cost) { int len = gas.size(); int ind = 0; int remain = 0; int hold = 0; bool flag = false; for(int i=0;i<len;i++){ int r = gas[i]-cost[i]; remain += r; if(flag == false && r > 0){ ind = i; flag = true; hold = hold + remain; remain = 0; } if(remain < 0) flag = false; } if(hold + remain >= 0) return ind; else return -1; } };
原文：http://www.cnblogs.com/code-swan/p/4139697.html