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Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

Question

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

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Solution

Sure, here is a Python solution using recursion and backtracking:

def permute(nums):
    def backtrack(first = 0):
        # if all integers are used up
        if first == n:  
            output.append(nums[:])
        for i in range(first, n):
            # place i-th integer first 
            # in the current permutation
            nums[first], nums[i] = nums[i], nums[first]
            # use next integers to complete the permutations
            backtrack(first + 1)
            # backtrack
            nums[first], nums[i] = nums[i], nums[first]
            
    n = len(nums)
    output = []
    backtrack()
    return output

Here's how it works:

  1. If all integers are used up, add the permutation to the output.
  2. Iterate over the integers from first to the end of array.
  3. Place the integer at index first that we're iterating on at the beginning of the permutation, i.e. swap(nums[first], nums[i]).
  4. Proceed to create all permutations which starts from first and keeps first+1 in the remaining part.
  5. Now we have to backtrack, so we swap the numbers back to restore the original array. We do this because we want to try a different possibility for the number at the first index.
  6. Repeat the process until we have found all permutations.

This problem has been solved

Similar Questions

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order. Example 1:Input: nums = [1,2,3]Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]Example 2:Input: nums = [0,1]Output: [[0,1],[1,0]]Example 3:Input: nums = [1]Output: [[1]] Constraints:1 <= nums.length <= 6-10 <= nums[i] <= 10All the integers of nums are unique.

A permutation of an array of integers is an arrangement of its members into a sequence or linear order.For example, for arr = [1,2,3], the following are all the permutations of arr: [1,2,3], [1,3,2], [2, 1, 3], [2, 3, 1], [3,1,2], [3,2,1].The next permutation of an array of integers is the next lexicographically greater permutation of its integer. More formally, if all the permutations of the array are sorted in one container according to their lexicographical order, then the next permutation of that array is the permutation that follows it in the sorted container. If such arrangement is not possible, the array must be rearranged as the lowest possible order (i.e., sorted in ascending order).For example, the next permutation of arr = [1,2,3] is [1,3,2].Similarly, the next permutation of arr = [2,3,1] is [3,1,2].While the next permutation of arr = [3,2,1] is [1,2,3] because [3,2,1] does not have a lexicographical larger rearrangement.Given an array of integers nums, find the next permutation of nums.The replacement must be in place and use only constant extra memory. Example 1:Input: nums = [1,2,3]Output: [1,3,2]Example 2:Input: nums = [3,2,1]Output: [1,2,3]Example 3:Input: nums = [1,1,5]Output: [1,5,1] Constraints:1 <= nums.length <= 1000 <= nums[i] <= 100

Given an n-digit number(all digits are unique), write a working  code to generate permutations of all numbers possible using one or more digits from the input number.Eg: Input: 123Output:123121321233132123132213231312321

Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once. The relative order of the elements should be kept the same. Then return the number of unique elements in nums.Consider the number of unique elements of nums to be k, to get accepted, you need to do the following things:Change the array nums such that the first k elements of nums contain the unique elements in the order they were present in nums initially. The remaining elements of nums are not important as well as the size of nums.Return k.Custom Judge:The judge will test your solution with the following code:int[] nums = [...]; // Input arrayint[] expectedNums = [...]; // The expected answer with correct lengthint k = removeDuplicates(nums); // Calls your implementationassert k == expectedNums.length;for (int i = 0; i < k; i++) { assert nums[i] == expectedNums[i];}If all assertions pass, then your solution will be accepted. Example 1:Input: nums = [1,1,2]Output: 2, nums = [1,2,_]Explanation: Your function should return k = 2, with the first two elements of nums being 1 and 2 respectively.It does not matter what you leave beyond the returned k (hence they are underscores).Example 2:Input: nums = [0,0,1,1,1,2,2,3,3,4]Output: 5, nums = [0,1,2,3,4,_,_,_,_,_]Explanation: Your function should return k = 5, with the first five elements of nums being 0, 1, 2, 3, and 4 respectively.It does not matter what you leave beyond the returned k (hence they are underscores). Constraints:1 <= nums.length <= 3 * 104-100 <= nums[i] <= 100nums is sorted in non-decreasing order.

PermutationWrite a C function that takes an array of digits representing a number and returns a 2D array containing all possible permutations of the digits.For example, given the array [1, 2, 3], the function should return a 2D array containing the following permutations: [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]].Testcase:Input:1 2 3Output:1 2 3 1 3 2 2 1 3 2 3 1 3 2 1 3 1 2

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