- Note: normally 2) and 3) are in reversed order; this problem is a bit different - This is efficient when the number of characters is not limited to 26, the runtime is still O(m + n) ...

// where 'n' is the length of 'nums'. // For each number in 'nums', we traverse each position for the permutations to add the number, // with each permutation being O(n!). // Space Complexity : O(n!), ...