This program illustrates the use of the STL prev_permutation() algorithm
(extended version) to generate all permutations of a vector of integers,
in decreasing order, and also to demonstrate what happens to the return
value of the algorithm when the "end" of a permutation sequence is reached
and we then "roll over" to begin a new sequence. In this case the order of
the integers in a permutation is determined by one integer preceding another
if and only if it has a larger digit sum.
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First, we declare a vector of 3 integers and show all of its permuations.
Here are the contents of the vector before any permutations are generated:
17 25 51
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And here are the contents of the vector as each permutation is generated:
17 51 25
25 17 51
25 51 17
51 17 25
51 25 17
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Finally (for this vector), here are its contents
after all permutations have been generated:
17 25 51
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Here are the contents of a second vector of 5 integers
before any permutations are generated:
55 25 51 17 11
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Now we show the return value of the algorithm, and the contents of
this vector, after each of 6 permutations of just the middle 3 values.
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Return value: true      Vector contents: 55 51 17 25 11
Return value: true      Vector contents: 55 51 25 17 11
Return value: false     Vector contents: 55 17 25 51 11
Return value: true      Vector contents: 55 17 51 25 11
Return value: true      Vector contents: 55 25 17 51 11
Return value: true      Vector contents: 55 25 51 17 11
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