[Swift]LeetCode1079. 活字印刷 | Letter Tile Possibilities
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You have a set of 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.
Example 1:
Input: "AAB"
Output: 8
Explanation: The possible sequences are "A", "B", "AA", "AB", "BA", "AAB", "ABA", "BAA".
Example 2:
Input: "AAABBC"
Output: 188
Note:
1 <= tiles.length <= 7tilesconsists of uppercase English letters.
你有一套活字字模 tiles，其中每个字模上都刻有一个字母 tiles[i]。返回你可以印出的非空字母序列的数目。
示例 1：
输入："AAB" 输出：8 解释：可能的序列为 "A", "B", "AA", "AB", "BA", "AAB", "ABA", "BAA"。
示例 2：
输入："AAABBC" 输出：188
提示：
1 <= tiles.length <= 7tiles由大写英文字母组成
Runtime: 12 ms
Memory Usage: 22.5 MB
1 class Solution { 2 func numTilePossibilities(_ tiles: String) -> Int { 3 let arr:[Character] = Array(tiles) 4 let len:Int = tiles.count 5 var cnt:[Character:Int] = [Character:Int]() 6 var ans:Int = 0 7 for i in 0..<len 8 { 9 cnt[arr[i],default: 0] += 1 10 } 11 var tab:[Int] = [Int]() 12 cnt.dropLast() 13 for val in cnt.values 14 { 15 tab.append(val) 16 } 17 dfs(&tab, &ans) 18 return ans 19 } 20 21 func dfs(_ tab:inout [Int],_ ans:inout Int) 22 { 23 for i in 0..<tab.count 24 { 25 if tab[i] > 0 26 { 27 ans += 1 28 tab[i] -= 1 29 dfs(&tab,&ans) 30 tab[i] += 1 31 } 32 } 33 } 34 } 35 36 //String扩展 37 extension String { 38 //subscript函数可以检索数组中的值 39 //直接按照索引方式截取指定索引的字符 40 subscript (_ i: Int) -> Character { 41 //读取字符 42 get {return self[index(startIndex, offsetBy: i)]} 43 } 44 }
20ms
1 class Solution { 2 var memo = [String:Int]() 3 func helper(_ tiles: String, _ n: Int) -> Int { 4 guard n > 0 else { return 1 } 5 var visited = Set<Character>() 6 var count = 0 7 for i in 0..<tiles.count { 8 let index = tiles.index(tiles.startIndex, offsetBy: i) 9 let char = tiles[index] 10 guard !visited.contains(char) else { continue } 11 visited.insert(char) 12 var newTiles = tiles 13 newTiles.remove(at: index) 14 let key = newTiles + String(n - 1) 15 if memo[key] == nil { 16 memo[key] = helper(newTiles, n - 1) 17 } 18 count += memo[key]! 19 } 20 return count 21 } 22 23 func numTilePossibilities(_ tiles: String) -> Int { 24 return (1...tiles.count) 25 .map { helper(tiles, $0) } 26 .reduce(0, +) 27 } 28 }
84ms
1 class Solution { 2 func helper(_ tiles: String, _ n: Int) -> Int { 3 guard n > 0 else { return 1 } 4 5 var visited = Set<Character>() 6 var count = 0 7 for i in 0..<tiles.count { 8 let index = tiles.index(tiles.startIndex, offsetBy: i) 9 let char = tiles[index] 10 guard !visited.contains(char) else { continue } 11 visited.insert(char) 12 var newTiles = tiles 13 newTiles.remove(at: index) 14 count += helper(newTiles, n - 1) 15 } 16 return count 17 } 18 19 func numTilePossibilities(_ tiles: String) -> Int { 20 var count = 0 21 for i in 1...tiles.count { 22 count += helper(tiles, i) 23 } 24 return count 25 } 26 }
116ms
1 class Solution { 2 3 func dfs( freq: inout [Character : Int]) -> Int { 4 var count = 0 5 6 for letter in freq { 7 if letter.value > 0 { 8 count += 1 9 freq[letter.key]! -= 1 10 count += dfs(freq: &freq) 11 freq[letter.key]! += 1 12 } 13 } 14 return count 15 } 16 17 func numTilePossibilities(_ tiles: String) -> Int { 18 var freq : [Character : Int] = [:] 19 for tile in tiles { 20 freq[tile, default:0] += 1 21 } 22 23 return dfs(freq: &freq) 24 } 25 }
204ms
1 class Solution { 2 func numTilePossibilities(_ tiles: String) -> Int { 3 var cache: Set<String> = Set<String>() 4 5 numFor(tile: tiles, cache: &cache) 6 7 return cache.count 8 } 9 10 private func numFor(tile: String, cache: inout Set<String>) { 11 // print("tile=\(tile), cache=\(cache)") 12 guard cache.contains(tile) == false else { 13 return 14 } 15 guard tile.count > 0 else { 16 return 17 } 18 19 cache.insert(tile) 20 21 for i in 1 ..< tile.count { 22 var temp = tile 23 let char = temp.remove(at: tile.index(tile.startIndex, offsetBy: i)) 24 numFor(tile: String(char), cache: &cache) 25 numFor(tile: temp, cache: &cache) 26 numFor(tile: String(char) + temp, cache: &cache) 27 } 28 } 29 }
212ms
1 class Solution { 2 func numTilePossibilities(_ tiles: String) -> Int { 3 var chars = Array(tiles) 4 var set = Set<String>() 5 var isVisited = [Bool](repeating: false, count: tiles.count) 6 var result = 0 7 findSeq(chars, &set, &isVisited, "") 8 // print(set) 9 return set.count 10 } 11 12 fileprivate func findSeq(_ chars: [Character], _ set: inout Set<String>, _ isVisited: inout [Bool], _ path: String) { 13 var count = 0 14 for item in isVisited { 15 if item == false { count += 1 } 16 } 17 if count == 0 { return } 18 19 20 for i in 0...chars.count-1 { 21 guard !isVisited[i] else { 22 continue 23 } 24 let curr = path + String(chars[i]) 25 if !set.contains(curr) { set.insert(curr) } 26 isVisited[i] = true 27 findSeq(chars, &set, &isVisited, curr) 28 isVisited[i] = false 29 } 30 } 31 }
224ms
1 class Solution { 2 var res = Set<String>() 3 func helper(_ chars: [Character], _ n: Int, _ selected: String) { 4 guard n > 0 else { 5 res.insert(selected) 6 return 7 } 8 for i in 0..<chars.count { 9 var newChars = chars 10 let newSelect = newChars.remove(at: i) 11 helper(newChars, n - 1, selected + String(newSelect)) 12 } 13 14 } 15 func numTilePossibilities(_ tiles: String) -> Int { 16 let chars = Array(tiles) 17 18 for i in 1...tiles.count { 19 helper(chars, i, "") 20 } 21 return res.count 22 } 23 }
232ms
1 class Solution { 2 private var sets = Set<String>() 3 func backtrack(_ chars: inout [Character], _ i: Int) { 4 if (i >= 1) { 5 let str = String(chars[0..<i]) 6 sets.insert(str) 7 } 8 if i == chars.count { return } 9 for j in i ..< chars.count { 10 chars.swapAt(i, j) 11 backtrack(&chars, i + 1) 12 chars.swapAt(i, j) 13 } 14 } 15 16 func numTilePossibilities(_ tiles: String) -> Int { 17 var chars = Array(tiles) 18 backtrack(&chars, 0) 19 return sets.count 20 } 21 }
