w3resource

JavaScript: Find the number of inversions of a specified array of integers

JavaScript Basic: Exercise-102 with Solution

Write a JavaScript program to find the number of inversions of a given array of integers.

Note: Two elements of the array a stored at positions i and j form an inversion if a[i] > a[j] and i < j.

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title> Find the number of inversions of a specified array of integers</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function number_of_InversionsNaive(arr) {
    var ctr = 0;
    for (var i = 0; i < arr.length; i++) {
        for (var j = i + 1; j < arr.length; j++) {
            if (arr[i] > arr[j]) 
              ctr++;
        }
    }
    return ctr;
}

console.log(number_of_InversionsNaive([0, 3, 2, 5, 9]));   
console.log(number_of_InversionsNaive([1, 5, 4, 3]));   
console.log(number_of_InversionsNaive([10, 30, 20, -10]));

Sample Output:

1
3
4

Flowchart:

Flowchart: JavaScript - Find the number of inversions of a specified array of integers

ES6 Version:

function number_of_InversionsNaive(arr) {
    let ctr = 0;
    for (let i = 0; i < arr.length; i++) {
        for (let j = i + 1; j < arr.length; j++) {
            if (arr[i] > arr[j]) 
              ctr++;
        }
    }
    return ctr;
}

console.log(number_of_InversionsNaive([0, 3, 2, 5, 9]));   
console.log(number_of_InversionsNaive([1, 5, 4, 3]));   
console.log(number_of_InversionsNaive([10, 30, 20, -10]));

Live Demo:

See the Pen javascript-basic-exercise-102 by w3resource (@w3resource) on CodePen.


Contribute your code and comments through Disqus.

Previous: Write a JavaScript program to check whether a given string contains only Latin letters and no two uppercase and no two lowercase letters are in adjacent positions.
Next: Write a JavaScript program to find the maximum number from a given positive integer by deleting exactly one digit of the given number.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



Share this Tutorial / Exercise on : Facebook and Twitter

JavaScript: Tips of the Day

Checks if a string is an anagram of another string (case-insensitive, ignores spaces, punctuation and special characters)

Example:

const isAnagram = (str1, str2) => {
  const normalize = str =>
    str
      .toLowerCase()
      .replace(/[^a-z0-9]/gi, '')
      .split('')
      .sort()
      .join('');
  return normalize(str1) === normalize(str2);
};
console.log(isAnagram('iceman', 'cinema')); // true

Output:

true