Initial data commit

Task/Longest-common-subsequence/Java/longest-common-subsequence-2.java

@@ -0,0 +1,31 @@
+public static String lcs(String a, String b) {
+    int[][] lengths = new int[a.length()+1][b.length()+1];
+
+    // row 0 and column 0 are initialized to 0 already
+
+    for (int i = 0; i < a.length(); i++)
+        for (int j = 0; j < b.length(); j++)
+            if (a.charAt(i) == b.charAt(j))
+                lengths[i+1][j+1] = lengths[i][j] + 1;
+            else
+                lengths[i+1][j+1] =
+                    Math.max(lengths[i+1][j], lengths[i][j+1]);
+
+    // read the substring out from the matrix
+    StringBuffer sb = new StringBuffer();
+    for (int x = a.length(), y = b.length();
+         x != 0 && y != 0; ) {
+        if (lengths[x][y] == lengths[x-1][y])
+            x--;
+        else if (lengths[x][y] == lengths[x][y-1])
+            y--;
+        else {
+            assert a.charAt(x-1) == b.charAt(y-1);
+            sb.append(a.charAt(x-1));
+            x--;
+            y--;
+        }
+    }
+
+    return sb.reverse().toString();
+}