#include <bits/stdc++.h>
#include<cstdio>
#include <queue>
#define pb push_back
#define mp make_pair
//Macro
#define eps 1e-9
#define pi acos(-1.0)
#define ff first
#define ss second
#define re return
#define QI queue
#define SI stack
#define SZ(x) ((int) (x).size())
#define all(x) (x).begin(), (x).end()
#define sq(a) ((a)*(a))
#define distance(a,b) (sq(a.x-b.x) + sq(a.y-b.y))
#define iseq(a,b) (fabs(a-b)<eps)
#define eq(a,b) iseq(a,b)
#define ms(a,b) memset((a),(b),sizeof(a))
#define G() getchar()
#define MAX3(a,b,c) max(a,max(b,c))
#define II ( { int a ; read(a) ; a; } )
#define LL ( { Long a ; read(a) ; a; } )
#define DD ({double a; scanf("%lf", &a); a;})

double const EPS=3e-8;
using namespace std;

#define FI freopen ("input_B.txt", "r", stdin)
#define FO freopen ("output_B.txt", "w", stdout)

typedef long long Long;
typedef long long int64;


//For loop

#define forab(i, a, b) for (__typeof (b) i = (a) ; i <= b ; ++i)
#define rep(i, n) forab (i, 0, (n) - 1)
#define For(i, n) forab (i, 1, n)
#define rofba(i, a, b) for (__typeof (b)i = (b) ; i >= a ; --i)
#define per(i, n) rofba (i, 0, (n) - 1)
#define rof(i, n) rofba (i, 1, n)
#define forstl(i, s) for (__typeof ((s).end ()) i = (s).begin (); i != (s).end (); ++i)
#define for1(i, a, b) for(int i=a; i<b; i++)

template< class T > T gcd(T a, T b) { return (b != 0 ? gcd(b, a%b) : a); }
template< class T > T lcm(T a, T b) { return (a / gcd(a, b) * b); }
#define __(args...) {dbg,args; cerr<<endl;}

#define __1D(a,n) rep(i,n) { if(i) printf(" ") ; cout << a[i] ; }
#define __2D(a,r,c,f) forab(i,f,r-!f){forab(j,f,c-!f){if(j!=f)printf(" ");cout<<a[i][j];}cout<<endl;}

signed main ()
{
    ios_base :: sync_with_stdio(0);cin.tie(0);cin.tie(0);

    int n;
    unsigned int a;
    priority_queue <unsigned int> pq;

    scanf("%d", &n);

    bool odd = (n%2==1);

    for(int i=n/2; i>=0; --i){
        scanf("%u", &a);
        pq.push(a);
    }
    n-=n/2+1;

    for(int i=0; i<n; i++){
        scanf("%u", &a);
        pq.push(a);
        pq.pop();
    }
    if(odd)printf("%u\n", pq.top());
    else{
        a=pq.top();
        pq.pop();

       // cout << fixed << setprecision(1) << (a+pq.top())/2.0 << endl;
       printf("%.1f\n", (a + pq.top() ) / 2.0);
    }
    return 0;
}

Priority queue uses vector under the hood.
How many times vector resized while first for() executed - unknown, what final vector capacity - unknown, was all vector buffers except last freed or they still kept by allocator - unknown.

I'd recommend to not use priority queue at all, I'd rather implement custom bike using fixed size buffer and std heap functions

There must be no problem with vector - I used it successfully but care about its size in advance (reserve and shrink). Be careful in printing big numbers (float not enough) and in using iterators - this is the problem of memory error could be - you may point to out of vector. Also different compilers use compile program with different size and use different allocators - try to use different compilers.