Question

I have an array of dictionary words and a random string like “twowords”

What is the fastest way to check if the entire string is made up of dictionary words? so “twojwords” would return false and “twowords” returns true

I was using a binary search before but it couldn’t handle two word strings

(I’m using objective c)

Answer 1

Here’s a naive approach, but I don’t know if there is a faster way.

for i1 from 0 to 6 do
  substring1 = string[0..i1];
  if (inDictionary(substring1)) {
    for i2 from i1+1 to 6 do
      substring2 = string[i1+1..i2];
      if (inDictionary(substring2)) {
        for i3 from i2+1 to 6 do 
... (up to i6)

For this, you need to be able to form a substring of letters a to b of the string. E.g. if string = "thisisastring" then string[4..7] = "isas". You also need a boolean function inDictionary, which should do a binary search for the substring in the dictionary.

This method will work, but depending on the size of the dictionary, may take a bit of time. I believe the English language is currently around 200000 words, in which case any reasonable programming language should have reasonable performance.