#0285

Permutations of Distinct Numbers

MediumDSA28 min20 XP

Problem

Given distinct numbers, return all permutations in lexicographic order.

Why This Matters

Permutations are the purest backtracking problem: choose an unused value, recurse, then undo.

Function Signature

def permutations(nums):

Examples

Example 1

Inputnums = [1,2,3]

Output[[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]

Every number gets a chance to appear in every position.

Constraints

Return the exact requested value.
Handle edge cases cleanly.
Use the intended DSA pattern when brute force would scale poorly.

CodePython

def permutations(nums):
    """
    Input example: nums = [1,2,3]
    Return: [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return []

def permutations(nums):
    """
    Input example: nums = [1,2,3]
    Return: [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return []

Visible browser tests run here when available.

Testcases2 visible / 3 hidden categories

Three numbers

Input[1,2,3]

Expectedsix permutations

3! equals 6.

Two numbers

Input[2,1]

Expected[[1, 2], [2, 1]]

Input is sorted first for stable output.

Hidden Test Categories

empty listsingle numberlarger distinct list