Question

How to count the total of all pairs permutations in an array with Node.js

Answer 1

const arr1 = [1, 8, 5];
 
// The pairs are: (1, 8), (1, 5), (8, 1), (8, 5), (5, 1), (5, 8)
 
let total_pairs = arr1.length * (arr1.length - 1);
console.log("Total Pairs = " + total_pairs);
 
const 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.length * (arr2.length - 1);
console.log("Total Pairs = " + total_pairs);
 
 
 
/*
run:
 
Total Pairs = 6
Total Pairs = 12
 
*/

 

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