From 4ef81a080d1fd0bafd8934fc2970d187c7ec2ba3 Mon Sep 17 00:00:00 2001
From: Vahagn Khachatryan <vahagn.khachatryan@gmail.com>
Date: Mon, 29 May 2017 07:39:38 +0100
Subject: [PATCH] puzzle: Number of valid combinations of strings for given
 input.

---
 puzzles/interviews/training/num_valid_comb.py | 35 +++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 puzzles/interviews/training/num_valid_comb.py

diff --git a/puzzles/interviews/training/num_valid_comb.py b/puzzles/interviews/training/num_valid_comb.py
new file mode 100644
index 0000000..cb77558
--- /dev/null
+++ b/puzzles/interviews/training/num_valid_comb.py
@@ -0,0 +1,35 @@
+#
+# The number of valid combinations of a strings for given input array a[],
+# where a=&gt;1, z =&gt; 26, and 0 &lt;= a[i] &lt;= 9
+#       {1,1,1} =&gt; {aaa, ak, ka} =&gt; 3
+#       {1,1,0} =&gt; {aj} =&gt; 1  "/>
+#
+
+
+def valid_comb_aux(s, p, b, e, dyn):
+    if b in dyn:
+        print("dyn", p)
+        return dyn[b]
+    if b == e:
+        print("fin", p)
+        return 1
+    count = 0
+    for i in range(b+1, e+1):
+        if 0 < int(s[b:i]) and int(s[b:i]) <= (ord('z')-ord('a')+1):
+            p.extend(chr(ord('a')+int(s[b:i])-1))
+            count = count + valid_comb_aux(s, p, i, e, dyn)
+            p.pop()
+    dyn[b] = count
+    return count
+
+
+def valid_comb(s):
+    dyn = {}
+    return valid_comb_aux(s, [], 0, len(s), dyn)
+
+
+if __name__ == "__main__":
+    print(valid_comb("111"))
+    print(valid_comb("110"))
+    print(valid_comb("22222"))
+    # valid_comb("12131456879234522222")