puzzle: Number of valid combinations of strings for given input.

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=>1, z => 26, and 0 <= a[i] <= 9
+#       {1,1,1} => {aaa, ak, ka} => 3
+#       {1,1,0} => {aj} => 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")