66. Count Pairs with Sum
MediumHash MapCounting
Count pairs of positions (i < j) with a[i] + a[j] = k.
Input format
Line 1: n k Line 2: n integers
Output format
The number of pairs.
Example 1
Input
4 6 1 5 7 1
Output
2
Example 2
Input
4 2 1 1 1 1
Output
6
Constraints
1 ≤ n ≤ 10⁵
Read input from standard input and print the answer to standard output. Your code is judged against 6 test cases, most of them hidden.
Loading the MyLoginn IDE…