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import std.stdio, std.algorithm, std.math;
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double entropy(T)(T[] s)
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/*pure nothrow*/ if (__traits(compiles, sort(s))) {
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return s
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.sort()
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.group
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.map!(g => g[1] / cast(double)s.length)
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.map!(p => -p * log2(p))
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.reduce!q{a + b};
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}
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void main() {
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"1223334444"d.dup.entropy.writeln;
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}
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