Question

How to count the total of all pairs permutations in an array with C++

Answer 1

#include <vector>
#include <iostream>

int main()
{
	std::vector<int> arr1 = {1, 8, 5};

	// The pairs are: (1, 8), (1, 5), (8, 1), (8, 5), (5, 1), (5, 8) 

	int total_pairs = arr1.size() * (arr1.size() - 1);
	std::cout << "Total Pairs = " << total_pairs << std::endl;

	std::vector<int> arr2 = {1, 8, 5, 2};

	// The pairs are: (1, 8), (1, 5), (1, 2), (8, 1), (8, 5), (8, 2), 
	//                (5, 1), (5, 8), (5, 2), (2, 1), (2, 8), (2, 5)

	total_pairs = arr2.size() * (arr2.size() - 1);
	std::cout << "Total Pairs = " << total_pairs << std::endl;
}



/*
run:

Total Pairs = 6
Total Pairs = 12

*/

 

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