This program illustrates the use of the STL next_permutation() algorithm
(extended version) to generate all permutations of a vector of integers,
in 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 smaller 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:
51 25 17
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And here are the contents of the vector as each permutation is generated:
51 17 25
25 51 17
25 17 51
17 51 25
17 25 51
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Finally (for this vector), here are its contents
after all permutations have been generated:
51 25 17
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Here are the contents of a second vector of 5 integers
before any permutations are generated:
11 25 17 51 55
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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: 11 17 51 25 55
Return value: true      Vector contents: 11 17 25 51 55
Return value: false     Vector contents: 11 51 25 17 55
Return value: true      Vector contents: 11 51 17 25 55
Return value: true      Vector contents: 11 25 51 17 55
Return value: true      Vector contents: 11 25 17 51 55
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