归并排序

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 = 0,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++];

for(i = l,j = 0;i <= r;i++,j++) q[i] = tmp[j];
}