Javascript Interview Question:Permutaions of string ( FreeCodeCamp)

Problem Statement:

Return the number of total permutations of the provided string that

don't have repeated consecutive letters. Assume that all characters

in the provided string are each unique.

For example, aab should return 2 because it has 6 total permutations

(aab, aab, aba, aba, baa, baa , but only 2 of them (aba and aba

don't have the same letter (in this case a repeating.

Test Cases:

Input "aab" should return 2

Input "aaa" should return 0

Input "aabb" should return 8

Input "abcdefa" should return 3600

Input "abfdefa" should return 2640

Input "zzzzzzzz" should return 0

Input "a" should return 1

Input "aaab" should return 0

Input "aaabb" should return 12

Solution:

function permute(str) {

let result = [];

if (str.length == 1) {

return [str];

}

for (let i = 0; i < str.length; i++) {

let firstElement = str.split("")[i]; //first element

//remaining element array

let remaining = str

.split("")

.filter((elem, index) => {

if (index != i) {

return true;

}

})

.join("");

let perms = permute(remaining);

for (let j = 0; j < perms.length; j++) {

perms[j] = perms[j] + firstElement;

}

result.push(...perms);

}

//remove element with same consecutative chars

let finalResult=[]

for (k = 0; k < result.length; k++) {

if(!findRepetation(result[k])){

finalResult.push(result[k])

}

}

return finalResult;

}

function findRepetation(str) {

for (let i = 0; i < str.length - 1; i++) {

let iThChar = str[i];

let iPlusOneThChar = str[i + 1];

if (iThChar == iPlusOneThChar) {

return true;

}

}

return false;

}

let str = "abfdefa";

let result = permute(str);

console.log("RESULT:",result);

console.log("Total Permutaions:",result.length);