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filling a vector with pairs

hi there,
I'm filling this vector with pages of a book.
float mid = (float)n / 2; // n = the number of pages int pages = 0; std::vector<pair<int, int>> pagesVec; for(int i = 0; i = mid; i++){ if(pages >= n){ pagesVec.emplace_back(pages , 0); // books holds an even number of pages, an empty page should be added. break; } else{ pagesVec.emplace_back(pages , pages++); pages++; } }
the problem is in the for loop definition.
for(int i = 0; i < n; i++){ // adds to many pages for(int i = 0; i < mid; i++){ // works pretty good, but ... for(int i = 0; i = mid; i++){
this is how it should look, but depending on the number of a pages a book has.
(empty,1)(2,3)(4,5) <  odd number of pages, no empty page on the back.
or
(empty,1)(2,3)(4,5)(6.empty) <  even number of pages, zero denotes empty pagewould anyone know a better way or more efficient to fill the vector of pairs with pages?
4 page book looks like this (good):
// using for(int i = 0; i = mid; i++){ first;1second: 0 first;3second: 2 first;4second: 0
a 5 page looks like this (good):
// using for(int i = 0; i < mid; i++){ first;1second: 0 first;3second: 2 first;5second: 4
a 5 page looks like this (bad):
// using for(int i = 0; i = mid; i++){ first;1second: 0 first;3second: 2 first;5second: 4 first;6second: 0 // to much
a 5 page looks like this (bad):
// using for(int i = 0; i = n; i++){ first;1second: 0 first;3second: 2 first;5second: 4 first;6second: 0
p.s. i don't get it, why the first pair, first value is 1 and the second is 0 "pages++"
kind regards.

@Natural_Bugger
I'm sorry I am not the brightest at understanding what people are trying to do from their explanations, and I don't get whatever your problem is here, but here are some observations about what is wrong in what you show:
float mid = (float)n / 2; // n = the number of pages
: There are never a "floating number of pages" in a book! Please makemid
anint
, you should have nofloat
s in your code. Depending on which way you want to round an odd or even number, you probably wantint mid = (n + 1) / 2
(round an odd up to half of the next even). 
for(int i = 0; i = mid; i++)
:i = mid
can never be correct. The middle argument in afor()
must always be a condition.for(int i = 0; i < mid; i++)
looks better. 
pagesVec.emplace_back(pages , pages++);
: You must never do this in C/C++. You cannot tell whether the first occurrence ofpages
here has the value ofpages
before or after the second argument,pages++
, has been evaluated.
I suspect you're making something much more complex than is needed? Why any
mid
at all? Don't you just want something like:for (int i = 1; i < n; i += 2) pagesVec.emplace_back(i  1, i);
EDIT let me see if I can understand what you want:
(empty,1)(2,3)(4,5) <  odd number of pages, no empty page on the back.
(empty,1)(2,3)(4,5)(6.empty) <  even number of pages, zero denotes empty pageIn the first case
n == 5
, in the secondn == 6
. So one way would be:if (n > 0) for (int i = 1; i <= n + 1; i += 2) pagesVec.emplace_back(i  1, (i <= n) ? i : 0);


@JonB said in filling a vector with pairs:
thnx very much for your answer
for (int i = 1; i <= n + 1; i += 2) pagesVec.emplace_back(i  1, (i <= n) ? i : 0);
that solved the issue