This program illustrates the use of the STL nth_element() algorithm (extended
version) to partition a vector of integers of size 12 around its 7th element.
The ranges on either side of this value may or may not be sorted, but the
algorithm does not guarantee this, and you should not expect it. In this case
the order of the elements is determined by one integer preceding another if
and only if it has a smaller digit sum.
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Here are the initial contents of the vector:
92 21 53 84 46 13 41 76 45 61 11 15
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Now we make the following call:
nth_element(v.begin(), v.begin()+6, v.end());
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And here are the contents of the vector partitioned around its 7th element:
11 21 13 41 15 61 53 45 46 92 84 76
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