Given an array A of integers and integer K, return the maximum S such that there exists i < j with A[i] + A[j] = S and S < K. If no i, j exist satisfying this equation, return -1.
Example 1: Input: A = [34,23,1,24,75,33,54,8], K = 60 Output: 58 Explanation: We can use 34 and 24 to sum 58 which is less than 60. Example 2: Input: A = [10,20,30], K = 15 Output: -1 Explanation: In this case it's not possible to get a pair sum less that 15.排序，然后双指针，向中间走。
class Solution { public int twoSumLessThanK(int[] A, int K) { Arrays.sort(A); int i = 0; int j = A.length - 1; int max = -1; while (i < j) { if (A[i] + A[j] < K) { max = Math.max(max, A[i] + A[j]); i++; } else { j--; } } return max; } }