Given a string S of distinct character size N and their corresponding frequency f[] i.e. character S[i[ has  f[i] frequency.

Your task is to build a Huffman tree to print all the Huffman codes in preorder traversal of the tree.

S = "abcdef"
f[] = {5, 9, 12, 13, 16, 45}
Output:
  0   100   101   1100   1101   111

Explanation:
Huffman codes will be:
  f : 0
 c : 100
 d : 101
 a : 1100
 b : 1101
 e : 111