problem: given an array of integers including positive and negative, a target value. find 2 numbers in the array such that the sum of the 2 numbers is the closest to the target value.

Solution: this can be solved in O(nlogn).

First, invest some time to sort the array, O(nlogn).

Then,

int min= Integer.MAX;while(i< j){   if(A[i]+ A[j]== T) return (i,j);   (A[i]+ A[j]- T> 0)? j--: i++;     }

find the closest sum to a target value