气死我了

很简单，就是换

先给你们看我源代码

#include<bits/stdc++.h>
using namespace std;
int main(){
    long long n,a[100005];
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    for(int i=2;i<=n;i+=2){
        cout<<a[i]<<" "<<a[i-1]<<" ";
    }
}

没看见n<=2*1e5

#include<bits/stdc++.h>
using namespace std;
int main(){
    long long n,a[200005];
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    for(int i=2;i<=n;i+=2){
        cout<<a[i]<<" "<<a[i-1]<<" ";
    }
}