1160. Letter Tile Possibilities¶

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1160. Letter Tile Possibilities

Medium

You have n  tiles, where each tile has one letter tiles[i] printed on it.

Return the number of possible non-empty sequences of letters you can make using the letters printed on those tiles.

Example 1:

Input: tiles = "AAB"
Output: 8
Explanation: The possible sequences are "A", "B", "AA", "AB", "BA", "AAB", "ABA", "BAA".

Example 2:

Input: tiles = "AAABBC"
Output: 188

Example 3:

Input: tiles = "V"
Output: 1

Constraints:

• 1 <= tiles.length <= 7
• tiles consists of uppercase English letters.

Solution¶

class Solution {
    public int numTilePossibilities(String tiles) {
        int[] freq = new int[26];
        for (char c : tiles.toCharArray()) freq[c - 'A']++;
        return solve(freq);
    }
    private int solve(int[] freq) {
        int count = 0;
        for (int i = 0; i < 26; i++) {
            if (freq[i] > 0) {
                freq[i]--;
                count += 1 + solve(freq);
                freq[i]++;
            }
        }
        return count;
    }
}

Complexity Analysis¶

• Time Complexity: O(?)
• Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here