leetcode-1492-TheKthFactorOfN.js

// https://leetcode.com/problems/the-kth-factor-of-n/

// p: 2 + ints
// r: 1 +int or // -1
// e:
// Example 1:

// Input: n = 12, k = 3
// Output: 3
// Explanation: Factors list is [1, 2, 3, 4, 6, 12], the 3rd factor is 3.
// Example 2:

// Input: n = 7, k = 2
// Output: 7
// Explanation: Factors list is [1, 7], the 2nd factor is 7.
// Example 3:

// Input: n = 4, k = 4
// Output: -1
// Explanation: Factors list is [1, 2, 4], there is only 3 factors. We should return -1.
/////////////////////////////////////// NOT FINISHED ///////////////////////////////////////
var kthFactor = function (n, k) {
  // find all factors of n => arr
  //// loop form 1 to n /2
  for (let i = 1; i <= Math.sqrt(n); i++) {
    n % i === 0 && k--;
    if (n % i === 0 && k === 0) return i;
  }

  for (let i = Math.floor(Math.sqrt(n)); i >= 1; i--) {
    n % (n / i) === 0 && k--;
    if (n % (n / i) === 0 && k === 0) return n / i;
  }
  return -1;
};

// kthFactor(12, 3);
kthFactor(4, 4);
kthFactor(24, 6);

// var kthFactor = function (n, k) {
//     // find all factors of n => arr
//     //// loop form 1 to n /2
//     let arrI = [];
//     for (let i = 1; i <= Math.sqrt(n); i++) {
//       if (n % i === 0) arrI.push(i);
//     }
//     // sort arr
//     const secondPartOfI = arrI.map((num) => n / num).reverse();
//     //   console.log(arrI.concat(secondPartOfI));

//     // return arr[k] or -1
//     //   console.log(arrI, arrI[arrI.length - 1], secondPartOfI, secondPartOfI[0]);

//     arrI =
//       arrI[arrI.length - 1] === secondPartOfI[0]
//         ? arrI.concat(secondPartOfI.slice(1))
//         : arrI.concat(secondPartOfI);
//     console.log(arrI[k - 1] ? arrI[k - 1] : -1);

//     return arrI[k - 1] ? arrI[k - 1] : -1;
//   };