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Construct DFA for strings not ending with "THE"
A Deterministic Finite automaton (DFA) is a five tuples
M=(Q, Σ, δ,q0,F)
Where,
- Q : Finite set called states.
- Σ : Finite set called alphabets.
- δ : Q × Σ → Q is the transition function.
- q0 ϵ Q is the start or initial state.
- F : Final or accept state.
Accept Strings which are not ending with "THE"
Observe whether the given string is ending with “the” or not.
The different notations of “the” which are avoided in the end of the string are as follows −
"tHE", "thE", "THE", "ThE", "THe", "The", "tHe" and "the"
These all strings are not accepted from alphabet (A-Z)
Let the initial state is q0
Consider 4 states q0, q1, q2 and q3.
Let’s take a variable named DFA which will be initially 0.
Whenever a transition is there, it will update the value of DFA with the number associated with the new state.
Example
If a transition occurs from state q0 to state q1 then the value of DFA will be updated to 1.
If a transition occurs from state q2 to state q3 then the value of DFA will be updated to 3.
In this way, apply this algorithm on the entire string and if it reaches the end, then reach state 0, 1 or 2. Thus, our string will be accepted. Otherwise, it won’t be accepted.
Case 1
Input − pQdfGTthe
Output − Not Accepted
Case 2
Input − ThesdGTYid
Output − ACCEPTED
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