51Nod 1001 数组中和等于K的数对

#include <iostream>
#include <algorithm>

using namespace std;

const int MAX = 5e5;
int arr[MAX];

int main()
{
int K, n;
cin >> K >> n;
for (int i = 0; i < n; i++)
cin >> arr[i];
bool flag = false;
sort(arr,arr + n);
for (int i = 0; i < n; i++)
{
if (arr[i] + arr[n-1] < K)
continue;
for (int j = i + 1; j < n && arr[i] + arr[j] <= K; j++)
{
if (arr[i] + arr[j] == K)
{
flag = true;
if (arr[i] <= arr[j])
{
cout << arr[i] << " " << arr[j] << endl;
}
else
{
cout << arr[j] << " " << arr[j] << endl;
}
}
}
}
if (!flag)
{
cout << "No solution\n";
return 0;
}
return 0;
}