reorg and add code for second edition

11_dynamic_programming/swift/01_longest_common_subsequence.swift

@@ -0,0 +1,40 @@
+import Foundation
+
+if wordA[i] == wordB[j] {
+    // The letters match
+    cell[i][j] = cell[i-1][j-1] + 1
+} else {
+    // The letters don't match.
+    cell[i][j] = max(cell[i-1][j], cell[i][j-1])
+}
+
+/* Working example for "play" with
+
+var wordA = "fish"
+var wordB = "hish"
+var cell : [[Int]] = Array(repeating: Array(repeating: 0, count: wordA.characters.count), count: wordB.characters.count)
+let wordAArray = wordA.characters.map { String($0) }
+let wordBArray = wordB.characters.map { String($0) }
+
+for i in 0...wordA.characters.count-1 {
+    for j in 0...wordB.characters.count-1 {
+        // The letters match
+        if wordAArray[i] == wordBArray[j] {
+            if i > 0 && j > 0 {
+                cell[i][j] = cell[i-1][j-1] + 1
+            } else {
+                cell[i][j] =  1
+            }
+        } else {
+            // The letters don't match.
+            if i > 0 && j > 0 {
+                cell[i][j] = max(cell[i-1][j], cell[i][j-1])
+            } else {
+               cell[i][j] = 0
+            }
+        }
+    }
+}
+
+*/
+