JavaScript: Find whether the members of a given array of integers is a permutation of numbers from 1 to a given integer

JavaScript Basic: Exercise-123 with Solution

Check if Array is Permutation of Numbers 1 to n

Write a JavaScript program to find out if the members of a given array of integers are a permutation of numbers from 1 to a given integer.

Visual Presentation:

Sample Solution:

JavaScript Code:

// Function to check if input array is a permutation of [1, 2, 3, ..., n]
function is_permutation(input_arr, n) {
    // Loop through each element from 1 to n
    for (var i = 0; i < n; i++) {
        // Check if the current element is not found in the input array
        if (input_arr.indexOf(i + 1) < 0) {
            return false; // If not found, it's not a permutation
        }
    }
    return true; // If all elements are found, it's a permutation
}

// Test cases
console.log(is_permutation([1, 2, 3, 4, 5], 5)); // Output: true (permutation of [1, 2, 3, 4, 5])
console.log(is_permutation([1, 2, 3, 5], 5));    // Output: false (not a permutation of [1, 2, 3, 4, 5]) 

Output:

true
false

Live Demo:

See the Pen javascript-basic-exercise-123 by w3resource (@w3resource) on CodePen.

Flowchart:

ES6 Version:

// Function to check if input array is a permutation of [1, 2, 3, ..., n]
const is_permutation = (input_arr, n) => {
    // Loop through each element from 1 to n
    for (let i = 0; i < n; i++) {
        // Check if the current element is not found in the input array
        if (input_arr.indexOf(i + 1) < 0) {
            return false; // If not found, it's not a permutation
        }
    }
    return true; // If all elements are found, it's a permutation
}

// Test cases
console.log(is_permutation([1, 2, 3, 4, 5], 5)); // Output: true (permutation of [1, 2, 3, 4, 5])
console.log(is_permutation([1, 2, 3, 5], 5));    // Output: false (not a permutation of [1, 2, 3, 4, 5])

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