leetcode1029

 class Solution(object):
     def twoCitySchedCost(self, costs: 'List[List[int]]') -> int:
         costs = sorted(costs,key = lambda x: abs(x[0]-x[1]),reverse=True)
         n = len(costs)
         allcosts = 0
         left = 0
         right = 0
         for i in range(n):
             if costs[i][0] <= costs[i][1] and left < n//2:
                 left += 1
                 allcosts += costs[i][0]
             else:
                 if right < n//2:
                     right += 1
                     allcosts += costs[i][1]
                 else:
                     left += 1
                     allcosts += costs[i][0]
         return allcosts

贪心思想：根据人距离A，B城市的费用的“差值”，从大到小排序。排的靠前的优先选择其费用低的城市。如果某个城市的人数已经达到1/2，则剩下的全部选择另外一个城市。这种方式的总体的费用最低。