leetcode 134. Gas Station

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题目链接：leetcode

思路：
贪婪

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class Solution(object):
    def canCompleteCircuit(self, gas, cost):        
        n = len(gas)
        dp = [gas[0] - cost[0]]
        for i in range(1,n):
            dp.append(dp[-1] + gas[i] - cost[i])
        if dp[-1] < 0:
            return -1
        return (dp.index(min(dp)) + 1 )%n

一个更清晰的solution：

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class Solution(object):
    def canCompleteCircuit(self, gas, cost):
        """
        :type gas: List[int]
        :type cost: List[int]
        :rtype: int
        """
        start, cur_sum, total_sum = 0, 0, 0
        
        for i in range(len(gas)):
          diff = gas[i]-cost[i]
          cur_sum += diff
          total_sum += diff
          
          if cur_sum < 0:
            start = i+1
            cur_sum = 0
        
        if total_sum >= 0:
          return start
        return -1