疑问

已AC（代码）（码风较丑，勿怪）

#include<iostream>
#include<cmath>
#include<cstdio>
#include<queue>
using namespace std;
const int N=1e5+5;
int n;
priority_queue<long long> da,xiao;
long long a[N],mid;
int main(){
    scanf("%d",&n);
    scanf("%lld",&a[1]);
    mid=a[1];da.push(a[1]);
    printf("%lld\n",a[1]);
    for(int i=2;i<=n;i++){
        scanf("%lld",&a[i]);
        if(a[i]>mid) xiao.push(-a[i]);
        else da.push(a[i]);
        while(da.size()>xiao.size()){xiao.push(-da.top());da.pop();}
        while(xiao.size()>da.size()){da.push(-xiao.top());xiao.pop();}
        if(da.size()>xiao.size()) mid=da.top();
        else mid=-xiao.top();
        if(i%2==1)printf("%lld\n",mid);
    }
    return 0;
}

while里改成>0就不运行了

#include<iostream>
#include<cmath>
#include<cstdio>
#include<queue>
using namespace std;
const int N=1e5+5;
int n;
priority_queue<long long> da,xiao;
long long a[N],mid;
int main(){
    scanf("%d",&n);
    scanf("%lld",&a[1]);
    mid=a[1];da.push(a[1]);
    printf("%lld\n",a[1]);
    for(int i=2;i<=n;i++){
        scanf("%lld",&a[i]);
        if(a[i]>mid) xiao.push(-a[i]);
        else da.push(a[i]);
        while(da.size()-xiao.size()>0){xiao.push(-da.top());da.pop();}
        while(xiao.size()-da.size()>0){da.push(-xiao.top());xiao.pop();}
        if(da.size()>xiao.size()) mid=da.top();
        else mid=-xiao.top();
        if(i%2==1)printf("%lld\n",mid);
    }
    return 0;
}