Add tasks for all the new languages

Task/Longest-common-subsequence/Nim/longest-common-subsequence-1.nim

@@ -0,0 +1,13 @@
+proc lcs(x, y): string =
+  if x == "" or y == "":
+    return ""
+
+  if x[0] == y[0]:
+    return x[0] & lcs(x[1..x.high], y[1..y.high])
+
+  let a = lcs(x, y[1..y.high])
+  let b = lcs(x[1..x.high], y)
+  result = if a.len > b.len: a else: b
+
+echo lcs("1234", "1224533324")
+echo lcs("thisisatest", "testing123testing")

Task/Longest-common-subsequence/Nim/longest-common-subsequence-2.nim

@@ -0,0 +1,28 @@
+proc lcs(a, b): string =
+  var ls = newSeq[seq[int]] a.len+1
+  for i in 0 .. a.len:
+    ls[i].newSeq b.len+1
+
+  for i, x in a:
+    for j, y in b:
+      if x == y:
+        ls[i+1][j+1] = ls[i][j] + 1
+      else:
+        ls[i+1][j+1] = max(ls[i+1][j], ls[i][j+1])
+
+  result = ""
+  var x = a.len
+  var y = b.len
+  while x > 0 and y > 0:
+    if ls[x][y] == ls[x-1][y]:
+      dec x
+    elif ls[x][y] == ls[x][y-1]:
+      dec y
+    else:
+      assert a[x-1] == b[y-1]
+      result = a[x-1] & result
+      dec x
+      dec y
+
+echo lcs("1234", "1224533324")
+echo lcs("thisisatest", "testing123testing")