求助，WA#9，AI、对拍均未找到准确错误原因

#include<iostream>
using namespace std;
long long p[500005],k;
long long a[500005],b[500005];
int n, m;
void merge(int l, int r, int m) {
	int i = l, j = m + 1, cnt = i;
	for (int i = l; i <= r; i++)b[i] = a[i];
	while (i <= m && j <= r) {
		if (b[i] <= b[j])a[cnt++] = b[i++];
		else a[cnt++] = b[j++];
	}
	while (i <= m)a[cnt++] = b[i++];
	while (j <= r)a[cnt++] = b[j++];
}
void mergesort(int l, int r) {
	if (l >= r)return;
	int mid = (l + r) / 2;
	mergesort(l, mid);
	mergesort(mid + 1, r);
	merge(l, r, mid);
}
bool check(int l,int r) {
	long long sum = 0;
	for (int i = 0; i < m && l + i < r - i; i++) {
		sum += (a[r - i] - a[l + i]) * (a[r - i] - a[l + i]);
	}
	if (sum <= k)return 1;
	else return 0;
}
int main() {
	int T;
	cin >> T;
	while (T--) {
		cin >> n >> m >> k;
		for (int i = 1; i <= n; i++) {
			cin >> p[i];
		}
		int s = 1, e = 0, ans = 0;
		while (s <= n) {
			int add=1;
			while (e < n) {//扩
				if (e + add > n)add = n - e;
				for (int i = e + 1; i <= e + add; i++) {
					a[i] = p[i];
				}
				mergesort(e + 1, e + add);
				merge(s, e + add, e);
				if (check(s, e + add)) {//继续扩
					for (int i = s; i <= e + add; i++) {
						p[i] = a[i];
					}
					e += add;
					add *= 2;
				}
				else {//开始缩
					add /= 2;
					break;
				}
			}
			while (add > 0 && e < n) {//缩
				if (e + add > n) {
					add /= 2;
					continue;
				}
				for (int i = s; i <= e+add; i++) {
					a[i] = p[i];
				}
				mergesort(e + 1, e + add);
				merge(s, e + add, e);
				if (check(s, e + add)) {
					for (int i = s; i <= e + add; i++) {
						p[i] = a[i];
					}
					e += add;
				}
				add /= 2;
			}
			s = e + 1;
			ans++;
		}
		cout << ans << endl;
	}
	return 0;
}