归并排序--acwing--经典模板

# include <iostream>
# include <stdlib.h>
using namespace std;

const int N = 1000010;

int n;
int q[N], tmp[N];

void merge_sort(int q[], int l, int r) {
	if (l >= r) return;
	int mid = l + r >> 1;
	merge_sort(q, l, mid), merge_sort(q, mid + 1, r);
	int k = l, i = l, j = mid + 1;
	while (i <= mid && j <= r) {
		if (q[i] < q[j]) tmp[k++] = q[i++];
		else tmp[k++] = q[j++];
	}
	while (i <= mid) tmp[k++] = q[i++];
	while (j <= r) tmp[k++] = q[j++];

	memcpy(q+l,tmp+l,sizeof(int) * (r-l+1));
}

int main() {
	scanf("%d", &n);
	for (int i = 0; i < n; i++) scanf("%d", &q[i]);
	merge_sort(q, 0, n - 1);
	for (int i = 0; i < n; i++) printf("%d", q[i]);

	system("pause");
	return 0;
}