原題地址:https://oj.leetcode.com/problems/gas-station/
題意:
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.
解題思路:這道題也很tricky,自己想是很難想出來的。如果sum(gas)<sum(cost)的話,那麼一定無解。diff是走完一站郵箱剩下的油,如果加上gas[i]也到不了下一站,那麼繼續將下一站設定為起點,然後再檢查,是不是很巧妙呢?
程式碼:
class Solution: # @param gas, a list of integers # @param cost, a list of integers # @return an integer def canCompleteCircuit(self, gas, cost): if sum(gas) < sum(cost): return -1 n = len(gas) diff = 0 stationIndex = 0 for i in range(n): if gas[i]+diff < cost[i]: stationIndex = i+1; diff = 0 else: diff += gas[i]-cost[i] return stationIndex