i learn vector. but have mistakes. i dont know where

UndefinedBehaviorSanitizer:DEADLYSIGNAL
==1==ERROR: UndefinedBehaviorSanitizer: SEGV on unknown address 0x000002ab1000 (pc 0x0000004256b0 bp 0x000002ab0ff8 sp 0x7ffe65674d90 T1)
==1==The signal is caused by a READ memory access.
==1==WARNING: invalid path to external symbolizer!
==1==WARNING: Failed to use and restart external symbolizer!
#include
#include
using namespace std;

vector pipe_fix(const vector& nums) {
//убрать повторения
vector nums1 = nums;

for ( vector::iterator i = nums1.begin(); i != nums1.end(); ++i)

for ( vector<int>::iterator j = i + 1;      j != nums1.end();  ++j)
  if ( *i == *j) {  nums1.erase(j); --j;  }

//и отсортировать
vector nums2(nums1.size()); // создаем новый вектор, там все будет отсортировано
int min = nums1[0];
vector::iterator it_min;
vector::iterator i = nums1.begin();
for ( ; i != nums1.end(); ++i)
{
for ( vector::iterator j = i+1; j != nums1.end() & i != j; ++j)
{
if ( *i < *j & *i <= min) { min = *i; it_min = i;}
if ( *i > *j & *j <= min) { min = *j; it_min = j; }
}
nums2.push_back(min);
nums1.erase(it_min);
}

nums2.push_back( *(nums.begin() ) );// в конец вектора добавляем оставшийся элемент - самый большой

//далее отсортирован и нет повторений
vector n;
n.push_back(nums2[0]);
for ( int q = 0; nums2[0] + q != *(nums2.end() - 1); ++q)
n.push_back(nums2[0] + q);

n.push_back( *(nums2.end() - 1 ));
return n;
}

O! thank you so much!!!!!!

WHAT THE PROPLEM?
In file included from main.cpp:6:
./solution.cpp:5:20: warning: comparison of integers of different signs: 'int' and 'std::__cxx11::basic_string<char, std::char_traits, std::allocator >::size_type' (aka 'unsigned long') [-Wsign-compare]
for(int i = 0; i < str.length() ; ++i)
~ ^ ~~~~~~~~~~~~
./solution.cpp:12:23: warning: comparison of integers of different signs: 'int' and 'std::__cxx11::basic_string<char, std::char_traits, std::allocator >::size_type' (aka 'unsigned long') [-Wsign-compare]
for( int i = 0; i < x.length() ; ++i )
~ ^ ~~~~~~~~~~
2 warnings generated.