Rotating Treap-- maintain the number of columns

https://www.luogu.org/problemnew/show/P3391

Knowledge Point: 1.split:. 1 2. Remove the split numerical ranking

　　　　2.merge

　　　　3. Intercept l - r this interval, the first cut l - 1 out, and then cut r - l +1 (r-l + 1 is not r)

code:

#include <bits/stdc++.h>
#define M 500002
using namespace std;
int n,m,root;
int tot = 0;
int lazy[M];
int head[M],cnt;
struct edge
{
    int to;
    int nxt;
}e[M * 2];
void add(int x,int y)
{
    e[++cnt].nxt = head[x];
    e[cnt].to = y;
    head[x] = cnt;
}
intsiz [M];
int ch [M] [ 2 ], val [M], rd [M];
void updata ( int x) 
{ 
    siz [x] = siz [ch [x] [ 0 ]] + siz [ch [x] [ 1 ]] + 1 ; 
} 
Int newnode ( int x) 
{ 
    val [ ++ tot] = x; 
    rd [tot] = rand (); 
    siz [tot] = 1 ;
    return tot; 
} 
Void down ( int x) 
{ 
    swap (ch [x] [ 0 ], ch [x] [ 1]);
    if(ch[x][0]) lazy[ch[x][0]] ^= 1;
    if(ch[x][1]) lazy[ch[x][1]] ^= 1;
    lazy[x] = 0;
}
void split(int now,int k,int &x,int &y)
{
    if(!now)
    {
        x = y = 0;
        return;
    }
    else
    {
        if(lazy[now])down(now);
        if(siz[ch[now][0]] < k)
        {
            x = now;
            split(ch[now][1],k - siz[ch[now][0]] - 1,ch[now][1],y);
        }
        else
        {
            y = now;
            split(ch[now][0],k,x,ch[now][0]);
        }
        updata(now);
    }
}
int merge(int A,int B)
{
    if(!A || !B)return A + B;
    if(rd[A] < rd[B])
    {
        if(lazy[A])down(A);
        ch[A][1] = merge(ch[A][1],B);
        updata(A);
        return A;   
    } 
    else
    {
        if(lazy[B])down(B);
        ch[B][0] = merge(A,ch[B][0]);
        updata(B);
        return B;
    }
}
void work(int x,int y)
{
    int a,b,c,d; 
    split(root,x - 1,a,b);
    split(b,y - x + 1,b,c);
    lazy[b] ^= 1;
    root = merge(a,merge(b,c));
}
void insert(int t)
{
    root = merge(root,newnode(t));
}
void print(int i)
{
    if(!i) return;
    if(lazy[i]) down(i);
    print(ch[i][0]);
    printf("%d ",val[i]);
    print(ch[i][1]);
}
int main()
{
    srand(1);
    scanf("%d%d",&n,&m);
    for(int i = 1;i <= n;i++)insert(i);
    int x,y;
    while(m--)
    {
        scanf("%d%d",&x,&y);
        work(x,y);
    }
    print(root);
    return 0;
}