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slow_coder4's blog

Help! set stl
By slow_coder4, history, 7 years ago, In English

How can find the value from set given an index. suppose our set is st. st.insert(2); st.insert(6); st.insert(1);

Now i want to know the value of index 2 from set. Is there any logarithmic away? Thanks advance .

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7 years ago, # |
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See here Your text to link here...

UPD: IGNORE

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7 years ago, # |
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You cannot do it with a set.

However, there is another data structure with can answer such queries. See this blog post.

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7 years ago, # |
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You can find in logarithmic time with policy based data structures. See my this comment.

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7 years ago, # |
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You can use a vector.

Let's define a vector S.

insert a value x like this : S.insert(lower_bound(S.begin( ),S.end( ),x),x);

find the position of x like this : pos = upper_bound(S.begin( ),S.end( ),x)-S.begin( )

The complexity of vector's INSERT can be seen as LOG . However , it's slower than set. And make sure that values in the vector are ordered at the beginning.

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