Permutations in Java: Explanation & Practice

Generate all permutations of an array

Problem summary

Given an array of distinct integers, return all possible permutations. A permutation is a rearrangement of all elements.

Starter code

public class Main {
    public static void main(String[] args) {
        int[] nums = {1, 2, 3};
        
        // Backtracking: try each unused element at each position
        // Use visited array or swap technique
        // Print all permutations
    }
}

Expected output and test cases

[1,2,3] → 6 permutations

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

[0,1] → 2 permutations
```
[0,1]
[1,0]
```
[1] → just [1]
```
[1]
```

Hints

For each position, try all unused elements
Mark element as used, recurse, then unmark (backtrack)
Base case: when current permutation has all elements
Total permutations = n!

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