General All Permutations
Given a string of unique letters, find all of its distinct permutations.
Permutation means arranging things with an order. For example, permutations of [1, 2] are [1, 2] and [2, 1]. Permutations are best visualized with trees.
The number of permutations is given by n! (we looked at factorial in Recursion Review). The way to think about permutation is to imagine you have a bag of 3 letters. Initially, you have 3 letters to choose from, you pick one out of the bag. Now you are left with 2 letters, you pick again now there's only 1 letter. The total number of choices is 3*2*1 = 6 (hence we have 6 leaf nodes in the above tree).
Input
letters: a string of unique letters
Output
all of its distinct permutations
Examples
Example 1:
Input:
letters = abc
Output: abc acb bac bca cab cba
Explanation:
All permutations.