Design DFA to check even number of 1s using 2 states.












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The alphabet is {0,1}. Zero 1s in the string should be rejected. This can be done easily using 3 states. Can this be done usinng 2 states?










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  • $begingroup$
    You need a start state and a state that says there are an odd number of $1$s. Since you are rejecting zero $1$s, the start state cannot correspond to the end state so you need at least $3$ states.
    $endgroup$
    – John Douma
    Jan 13 at 7:06
















0












$begingroup$


The alphabet is {0,1}. Zero 1s in the string should be rejected. This can be done easily using 3 states. Can this be done usinng 2 states?










share|cite|improve this question









$endgroup$












  • $begingroup$
    You need a start state and a state that says there are an odd number of $1$s. Since you are rejecting zero $1$s, the start state cannot correspond to the end state so you need at least $3$ states.
    $endgroup$
    – John Douma
    Jan 13 at 7:06














0












0








0





$begingroup$


The alphabet is {0,1}. Zero 1s in the string should be rejected. This can be done easily using 3 states. Can this be done usinng 2 states?










share|cite|improve this question









$endgroup$




The alphabet is {0,1}. Zero 1s in the string should be rejected. This can be done easily using 3 states. Can this be done usinng 2 states?







computer-science automata






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asked Jan 13 at 6:57









user415612user415612

1




1












  • $begingroup$
    You need a start state and a state that says there are an odd number of $1$s. Since you are rejecting zero $1$s, the start state cannot correspond to the end state so you need at least $3$ states.
    $endgroup$
    – John Douma
    Jan 13 at 7:06


















  • $begingroup$
    You need a start state and a state that says there are an odd number of $1$s. Since you are rejecting zero $1$s, the start state cannot correspond to the end state so you need at least $3$ states.
    $endgroup$
    – John Douma
    Jan 13 at 7:06
















$begingroup$
You need a start state and a state that says there are an odd number of $1$s. Since you are rejecting zero $1$s, the start state cannot correspond to the end state so you need at least $3$ states.
$endgroup$
– John Douma
Jan 13 at 7:06




$begingroup$
You need a start state and a state that says there are an odd number of $1$s. Since you are rejecting zero $1$s, the start state cannot correspond to the end state so you need at least $3$ states.
$endgroup$
– John Douma
Jan 13 at 7:06










1 Answer
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$begingroup$

How about $s_0rightarrow_0 s_0$, $s_0rightarrow_1 s_1$, and $s_1rightarrow_{0,1} s_1$ with start state $s_0$ and end state $s_1$.



Ahh, okay. Sorry for misunderstanding. An even number of 1's. Then the automaton looks as follows:



$s_0rightarrow_0 s_0$, $s_0rightarrow_1 s_1$, $s_1rightarrow_0 s_1$, and $s_1rightarrow_{1} s_0$, where $s_0$ is the starting and ending state.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    In the title the OP requires also an even number of 1s, not just a non-zero number.
    $endgroup$
    – Peter Leupold
    Jan 14 at 19:37










  • $begingroup$
    "Zero 1s in the string should be rejected". This will accept 0.
    $endgroup$
    – user415612
    Jan 15 at 18:25











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1 Answer
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1 Answer
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active

oldest

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active

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active

oldest

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1












$begingroup$

How about $s_0rightarrow_0 s_0$, $s_0rightarrow_1 s_1$, and $s_1rightarrow_{0,1} s_1$ with start state $s_0$ and end state $s_1$.



Ahh, okay. Sorry for misunderstanding. An even number of 1's. Then the automaton looks as follows:



$s_0rightarrow_0 s_0$, $s_0rightarrow_1 s_1$, $s_1rightarrow_0 s_1$, and $s_1rightarrow_{1} s_0$, where $s_0$ is the starting and ending state.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    In the title the OP requires also an even number of 1s, not just a non-zero number.
    $endgroup$
    – Peter Leupold
    Jan 14 at 19:37










  • $begingroup$
    "Zero 1s in the string should be rejected". This will accept 0.
    $endgroup$
    – user415612
    Jan 15 at 18:25
















1












$begingroup$

How about $s_0rightarrow_0 s_0$, $s_0rightarrow_1 s_1$, and $s_1rightarrow_{0,1} s_1$ with start state $s_0$ and end state $s_1$.



Ahh, okay. Sorry for misunderstanding. An even number of 1's. Then the automaton looks as follows:



$s_0rightarrow_0 s_0$, $s_0rightarrow_1 s_1$, $s_1rightarrow_0 s_1$, and $s_1rightarrow_{1} s_0$, where $s_0$ is the starting and ending state.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    In the title the OP requires also an even number of 1s, not just a non-zero number.
    $endgroup$
    – Peter Leupold
    Jan 14 at 19:37










  • $begingroup$
    "Zero 1s in the string should be rejected". This will accept 0.
    $endgroup$
    – user415612
    Jan 15 at 18:25














1












1








1





$begingroup$

How about $s_0rightarrow_0 s_0$, $s_0rightarrow_1 s_1$, and $s_1rightarrow_{0,1} s_1$ with start state $s_0$ and end state $s_1$.



Ahh, okay. Sorry for misunderstanding. An even number of 1's. Then the automaton looks as follows:



$s_0rightarrow_0 s_0$, $s_0rightarrow_1 s_1$, $s_1rightarrow_0 s_1$, and $s_1rightarrow_{1} s_0$, where $s_0$ is the starting and ending state.






share|cite|improve this answer











$endgroup$



How about $s_0rightarrow_0 s_0$, $s_0rightarrow_1 s_1$, and $s_1rightarrow_{0,1} s_1$ with start state $s_0$ and end state $s_1$.



Ahh, okay. Sorry for misunderstanding. An even number of 1's. Then the automaton looks as follows:



$s_0rightarrow_0 s_0$, $s_0rightarrow_1 s_1$, $s_1rightarrow_0 s_1$, and $s_1rightarrow_{1} s_0$, where $s_0$ is the starting and ending state.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Jan 15 at 8:47

























answered Jan 13 at 8:00









WuestenfuxWuestenfux

5,1271513




5,1271513












  • $begingroup$
    In the title the OP requires also an even number of 1s, not just a non-zero number.
    $endgroup$
    – Peter Leupold
    Jan 14 at 19:37










  • $begingroup$
    "Zero 1s in the string should be rejected". This will accept 0.
    $endgroup$
    – user415612
    Jan 15 at 18:25


















  • $begingroup$
    In the title the OP requires also an even number of 1s, not just a non-zero number.
    $endgroup$
    – Peter Leupold
    Jan 14 at 19:37










  • $begingroup$
    "Zero 1s in the string should be rejected". This will accept 0.
    $endgroup$
    – user415612
    Jan 15 at 18:25
















$begingroup$
In the title the OP requires also an even number of 1s, not just a non-zero number.
$endgroup$
– Peter Leupold
Jan 14 at 19:37




$begingroup$
In the title the OP requires also an even number of 1s, not just a non-zero number.
$endgroup$
– Peter Leupold
Jan 14 at 19:37












$begingroup$
"Zero 1s in the string should be rejected". This will accept 0.
$endgroup$
– user415612
Jan 15 at 18:25




$begingroup$
"Zero 1s in the string should be rejected". This will accept 0.
$endgroup$
– user415612
Jan 15 at 18:25


















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