leetcode1099

 1 import sys
 2 class Solution:
 3     def twoSumLessThanK(self, A: 'List[int]', K: int) -> int:
 4         A.sort()
 5         n = len(A)
 6         if n == 1:
 7             return -1
 8         if n == 2:
 9             return A[0] + A[1] if A[0] + A[1] < K else -1
10         i,j = 0,n-1
11         mindiff = sys.maxsize
12         minsum = -1
13         while i < j:
14             cursum = A[i] + A[j]
15             if cursum < K:
16                 diff = K - cursum
17                 if diff < mindiff:
18                     mindiff = diff
19                     minsum = cursum
20                 i += 1
21             else:
22                 j -= 1
23         return minsum

思路：双指针，先将数组排序，在从两边向中间移动，每次计算与K的差值，保存最小的差值时两个数的和。