Generate All Permutations of Array in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start the permutation generation by calling the helper function.

DSA Typescript

function permute(nums: number[]): number[][] {
  const result: number[][] = [];
  function backtrack(start: number) {
    // helper function body
  }
  [1];
  return result;
}

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Abacktrack(0)

Bbacktrack(nums.length)

Cbacktrack(-1)

Dbacktrack()

Attempts:

3 left

💡 Hint

Common Mistakes

Calling backtrack with the length of the array instead of 0.

Calling backtrack without any argument.

Starting from a negative index.

We start generating permutations from index 0, so calling backtrack(0) initiates the process correctly.

2fill in blank

medium

Complete the code to swap elements at two indices in the array.

DSA Typescript

function swap(nums: number[], i: number, j: number): void {
  const temp = nums[i];
  nums[i] = nums[[1]];
  nums[[1]] = temp;
}

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A0

Bj

Cnums.length - 1

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using i instead of j for the second index.

Using a fixed index like 0 or nums.length - 1.

To swap elements at indices i and j, we assign nums[i] = nums[j] and nums[j] = temp.

3fill in blank

hard

Fix the error in the base case condition to add a copy of the current permutation to the result.

DSA Typescript

function permute(nums: number[]): number[][] {
  const result: number[][] = [];
  function backtrack(start: number) {
    if (start [1] nums.length) {
      result.push([...nums]);
      return;
    }
    // rest of code
  }
  backtrack(0);
  return result;
}

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A>

B<

C===

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using less than or greater than instead of equality.

Using less than or equal which triggers too early.

The base case is when start equals nums.length, meaning a full permutation is formed.

4fill in blank

hard

Fill both blanks to complete the for loop and swap calls inside the backtrack function.

DSA Typescript

function backtrack(start: number) {
  if (start === nums.length) {
    result.push([...nums]);
    return;
  }
  for (let i = [1]; i < nums.length; i++) {
    swap(nums, start, i);
    backtrack([2]);
    swap(nums, start, i);
  }
}

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Astart

Bi

Cstart + 1

Di + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Starting loop from 0 instead of start.

Calling backtrack with i instead of start + 1.

The loop starts from 'start' index, and after swapping, we recurse with start + 1 to fix the next position.

5fill in blank

hard

Fill all three blanks to complete the full permutation function with swap helper.

DSA Typescript

function permute(nums: number[]): number[][] {
  const result: number[][] = [];
  function swap(arr: number[], i: number, j: number): void {
    const temp = arr[i];
    arr[i] = arr[[1]];
    arr[[2]] = temp;
  }
  function backtrack(start: number) {
    if (start === nums.length) {
      result.push([...nums]);
      return;
    }
    for (let i = [3]; i < nums.length; i++) {
      swap(nums, start, i);
      backtrack(start + 1);
      swap(nums, start, i);
    }
  }
  backtrack(0);
  return result;
}

Drag options to blanks, or click blank then click option'

Aj

Bi

Cstart

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up i and j in swap assignments.

Starting loop from 0 instead of start.

In swap, we assign arr[i] = arr[j] and arr[j] = temp. The loop in backtrack starts from 'start' index.