反向扫描

#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
using LL = long long;
const int N = 1e6 + 10;

int a[N];

int main(){
    int n,m;
    while(cin>>a[n],a[n]) n++;
    cin>>m;

    sort(a,a+n);

    int i=0,j=n-1;
    while(i<j){
        int sum=a[i]+a[j];
        if(sum>m) j--;
        if(sum<m) i++;
        if(sum==m){
            cout<<a[i]<<' '<<a[j]<<'\n';
            i++;
        }
    }

    return 0;
}