1 class Solution {
 2     func strangePrinter(_ s: String) -> Int {
 3         var c = [Character]()
 4         var pre : Character = " "
 5         for (_, char) in s.enumerated() {
 6             if char != pre {
 7                 c.append(char)
 8                 pre = char
 9             }
10         }
11         var l = [[Int]](repeating:[Int](repeating: 0, count:c.count) , count:c.count)
12         return turn(c, 0, c.count - 1, &l)
13     }
14
15     func turn(_ c: [Character], _ i: Int, _ j: Int, _ l: inout [[Int]]) -> Int {
16         if i > j {
17             return 0
18         }
19         if l[i][j] > 0 {
20             return l[i][j]
21         }
22         var ans = turn(c, i, j-1, &l) + 1
23         for k in i ..< j {
24             if c[k] == c[j] {
25                 ans = min(ans, turn(c, i, k, &l) + turn(c, k+1, j-1, &l))
26             }
27         }
28         l[i][j] = ans
29         return ans
30     }
31 }

 1 class Solution {
 2     func strangePrinter(_ s: String) -> Int {
 3         if s.isEmpty {return 0}
 4         var arr:[Character] = Array(s)
 5         var n:Int = s.count
 6         var dp:[[Int]] = [[Int]](repeating:[Int](repeating:0,count:n),count:n)
 7         for i in (0...(n - 1)).reversed()
 8         {
 9             if(n < i) {continue}
10             for j in i..<n
11             {
12                 dp[i][j] = (i == j) ? 1 : (1 + dp[i + 1][j])
13                 if(j < i + 1) {continue}
14                 for k in (i + 1)...j
15                 {
16                     if arr[k] == arr[i]
17                     {
18                         dp[i][j] = min(dp[i][j], dp[i + 1][k - 1] + dp[k][j])
19                     }
20                 }
21             }
22         }
23         return (n == 0) ? 0 : dp[0][n - 1]
24     }
25 }