快速排序的最坏时间复杂度是多少？

const int N=1e5+5;int cnt=0,a[N],b[N];void merge_sort(int l , int r) {

if(l>=r) return;

int mid = (l+r) / 2 ;

merge_sort(l , mid);

merge_sort(mid+1 , r);

int i = l;

int p = l , q = mid+1;

while(p<=mid || q<=r) {

if(q>r || (p<=mid && a[p]<=a[q]))

b[i++] = a[p++];

else {

b[i++] = a[q++];

cnt += mid -p + 1;

}

}

for(i = l ; i <= r; i++)

a[i] = b[i];}int main() {

a[1]=1,a[2]=3,a[3]=2,a[4]=4;

merge_sort(1,4);

printf("%d\n",cnt);}