# RE Ques

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Describe in simple English the language represented by the regular expression r=(1+10)*
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can not starts with 0 and no two consecutive 0
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Brother suppose we have to do the reverse of the above lang that is derive the RE,then what steps should be followed?
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steps:-

1) Draw the DFA of RE which represent L

2) if more than one final states present in your DFA, make one Final states using ∈ transitions

3) interchange the initial state and final state

4) Change the direction of each edge

5) may be it leads to NFA, so convert into DFA

6) obtain the RE from DFA which is your required RE of LR.

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@Shaik Masthan,Brother one more thing why have we used a + and not concatenation?
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@Shaik Masthan,If you see there is a + b/w 1 and 10. This I am asking?
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concatenation means should be occur ( order should be preserved )

+ means only one of the those occur

a.b means first a occur then b occur

a+b means either a occur or b occur but not both

These operators are use by us.... on the requirement of us only

coming to your example (1+10)* can generate 1,11,11 and many more

but (1.10)* can not generate those strings, it will generates only 110,110110,110110110,..... only
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@Shaik Masthan,This is what I was actually looking for since yesterday. A big Thanks. :)

L =  language containing all strings over 0,1 except string starting from 0 and containing consecutive 0's
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Starting with 1 and no two consecutive 0's
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@arvin,Yeah true.

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