Why swap() function can't work with vector's iterator?

Question

I just can't undestand why swap() function can't work? It also receives two iterators. Can anyone tell me the reason?

#include <iostream> #include <vector> using namespace std; int main() { vector<int> vt; vt.push_back(0); vt.push_back(1); vector<int>::iterator it1 = vt.begin(); vector<int>::iterator it2 = ++vt.begin(); cout << vt[0]; // 0 cout << vt[1] << endl; // 1 swap(it1, it2); cout << vt[0]; // still 0 cout << vt[1] << endl; // still 1 system("pause"); return 0; }

"[swap()] receives two iterators" - no it doesn't. Look at it again more carefully. It receives two references to values, not iterators. — Remy Lebeau
– Remy Lebeau, Commented Aug 29, 2018 at 14:56

Remy Lebeau · Accepted Answer · 2018-08-29 14:58:16Z

swap() literally swaps what is passed to it. In your case, it is swapping it1 and it2 themselves, not the content they "point" to. You can use std::iter_swap() instead to swap the content that two iterators "point" to.

delta · Accepted Answer · 2018-08-29 05:49:14Z

2

swap swaps iterator not the content iterator points to. what you need is iter_swap.

answered Aug 29, 2018 at 5:49

delta

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Comments

Jie.Wang · Accepted Answer · 2018-08-29 06:41:54Z

You can try it like this

The pointer values *a and *b use be iterator with swap.

swap(*it1, *it2);

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