C - Boats Competition

一定要记得排序！

#include <iostream>
#include <algorithm>
using namespace std;
const int N = 60;
int n;
int a[N];
int main () {
	int T;
	cin >> T;
	while (T--) {
		cin >> n;
		for (int i = 1;i <= n;i++) cin >> a[i];
		sort (a+1,a+1+n);
		int ans = 0;
		for (int i = 2;i <= 2*n;i++) {
			int l = 1,r = n;
			int res = 0;
			while (l < r) {
				if (a[l]+a[r] == i) {
					res++;
					l++,r--;
				}
				else if (a[l]+a[r] > i) r--;
				else l++;
			}
			ans = max (ans,res);
		}
		cout << ans << endl;
	}
	return 0;
}