leetcode：greedy：Gas Station（134）

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.

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http://blog.csdn.net/lanxu_yy/article/details/17241891

class Solution {  public:      int canCompleteCircuit(vector<int> &gas, vector<int> &cost) {          vector<int> remainder;          int sum =0;          for(int i = 0; i < gas.size(); i++)          {              remainder.push_back(gas[i]-cost[i]);              sum += gas[i]-cost[i];          }          if(sum < 0)          {              return -1;          }          else          {              int start;              int cur = 0;              do              {                  start = cur;                  int tmp = remainder[cur++];                  while(tmp >= 0 && cur<gas.size())                  {                      tmp += remainder[cur++];                      if(tmp < 0)                      {                          break;                      }                  }                  if(tmp >= 0 && cur == gas.size())                  {                      return start;                  }              }while(cur<gas.size());              return -1;          }      }  };