Editing Lempel–Ziv–Welch (section)

===Decoding===
A high-level view of the decoding algorithm is shown here:
# Initialize the dictionary to contain all strings of length one.
# Read the next encoded symbol: Is it encoded in the dictionary?
##Yes:
###Emit the corresponding string '''W''' to output.
###Concatenate the previous string emitted to output with the first symbol of '''W'''. Add this to the dictionary.
##No:
###Concatenate the previous string emitted to output with its first symbol. Call this string '''V'''.
###Add '''V''' to the dictionary and emit '''V''' to output.
#Repeat Step 2 until end of input string
The decoding algorithm works by reading a value from the encoded input and outputting the corresponding string from the dictionary. However, the full dictionary is not needed, only the initial dictionary that contains single-character strings (and that is usually [[Hard coding|hard coded]] in the program, instead of sent with the encoded data). Instead, the full dictionary is rebuilt during the decoding process the following way: after decoding a value and outputting a string, the decoder [[concatenation|concatenates]] it with the first character of the ''next'' decoded string (or the first character of current string, if the next one can't be decoded; since if the next value is unknown, then it must be the value added to the dictionary in ''this'' iteration, and so its first character is the same as the first character of the current string), and updates the dictionary with the new string. The decoder then proceeds to the next input (which was already read in the previous iteration) and processes it as before, and so on until it has exhausted the input stream.