4. (10 points) You are given a string of n characters s[1..n], which you believe to be a piece of encrypted text. You wish to decipher the document using a code book, which is available in the form of a function decipher(-): for any string w, f(w) if w is a valid codeword (f (w) is the deciphered text in this case) decipher(w) = nul otherwise Design a dynamic programming algorithm that determines whether the string s[1..n] can be deciphered. Assume that each call to decipher takes unit time. Explain your design and the running time of your algorithm. 4. (10 points) You are given a string of n characters s[1..n], which you believe to be a piece of encrypted text. You wish to decipher the document using a code book, which is available in the form of a function decipher(-): for any string w, f(w) if w is a valid codeword (f (w) is the deciphered text in this case) decipher(w) = nul otherwise Design a dynamic programming algorithm that determines whether the string s[1..n] can be deciphered. Assume that each call to decipher takes unit time. Explain your design and the running time of your algorithm