Count Pairs With a Sum

Count the pairs of different positions i < j in numbers where numbers[i] + numbers[j] equals target. Use two nested loops.

Implement count_pairs_with_sum(numbers, target).

Input

numbers: The list of integers. target: The sum to look for.

Output

Return the number of pairs.

Restricciones

0 ≤ length of numbers ≤ 500; -10,000 ≤ each number, target ≤ 10,000

Ejemplos

Entrada:
target = 6
numbers = [1, 5, 3, 3, 4]

Salida esperada:
expected = 2

Entrada:
long long target = 6;
std::vector<long long> numbers = {1, 5, 3, 3, 4};

Salida esperada:
long long expected = 2;

Entrada:
long target = 6;
long[] numbers = new long[] {1, 5, 3, 3, 4};

Salida esperada:
long expected = 2;

Entrada:
target = 4
numbers = [2, 2, 2]

Salida esperada:
expected = 3

Entrada:
long long target = 4;
std::vector<long long> numbers = {2, 2, 2};

Salida esperada:
long long expected = 3;

Entrada:
long target = 4;
long[] numbers = new long[] {2, 2, 2};

Salida esperada:
long expected = 3;

Referencias

Este reto está adaptado para CodeUtility. Sigue el enunciado y las restricciones indicadas arriba.

• UW TCSS 142 Introduction to Programming - master syllabus