BZOJ 3223 Tyvj 1729 文艺平衡树 | Splay 维护序列关系

题解:

每次reverse(l,r)

把l-1转到根,r+1变成他的右儿子,给r+1的左儿子打个标记就是一次反转操作了

每次find和dfs输出的时候下放标记,把左儿子和右儿子换一下

记得建树的时候建0到n+1

#include<cstdio>
#include<algorithm>
#include<cstring>
#define N 100010
#define which(x) (ls[fa[(x)]]==(x))
using namespace std;
int sz[N],ls[N],rs[N],fa[N],n,m,root,flag[N],id[N],idx;
void upt(int x) {sz[x]=1+sz[ls[x]]+sz[rs[x]];}
int read()
{
    int ret=0,neg=1;
    char j=getchar();
    for (;j>'9' || j<'0';j=getchar())
    if (j=='-') neg=-1;
    for (;j>='0' && j<='9';j=getchar())
    ret=ret*10+j-'0';
    return ret*neg;
}
void write(int x)
{
    if (x<0) x=-x;
    if (x>=10) write(x/10);
    putchar(x%10+'0');
}
void swap_son(int u)
{
    if (!u) return;
    flag[u]^=1;
    swap(ls[u],rs[u]);
    upt(u);
}
void pushdown(int u)
{
    if (!flag[u]) return ;
    swap_son(ls[u]),swap_son(rs[u]);
    flag[u]=0;
}
int Build(int l, int r)
{
    int mid=l+r>>1,u=++idx;
    id[u]=mid;
    if(mid>l) ls[u]=Build(l,mid-1),fa[ls[u]]=u;
    if(mid<r) rs[u]=Build(mid+1,r),fa[rs[u]]=u;
    upt(u);
    return u;
}
void Rotate(int u)
{
    int v=fa[u],w=fa[v],b=which(u)?rs[u]:ls[u];
    if(w) which(v)?ls[w]=u:rs[w]=u;
    which(u)?(ls[v]=b,rs[u]=v):(rs[v]=b,ls[u]=v);
    fa[u]=w,fa[v]=u;
    if(b) fa[b]=v;
    upt(v),upt(u);
}
void Splay(int u, int tar)
{
    while(fa[u] != tar)
    {
    if(fa[fa[u]] != tar)
    {
        if(which(u) == which(fa[u])) Rotate(fa[u]);
        else Rotate(u);
    }
    Rotate(u);
    }
    if(!tar) root = u;
}
int find(int k)
{
    int u=root;
    pushdown(u);
    while (sz[ls[u]]+1!=k && u)
    {
    if (sz[ls[u]]>=k) u=ls[u];
    else k-=sz[ls[u]]+1,u=rs[u];
    pushdown(u);
    }
    return u;
}
void rev(int l,int r)
{
    int u=find(l-1),v=find(r+1);
    Splay(u,0);
    Splay(v,u);
    swap_son(ls[rs[root]]);
}
void dfs(int u)
{
    pushdown(u);
    if (ls[u]) dfs(ls[u]);
    if (id[u]>1 && id[u]<n+2) write(id[u]-1),putchar(' ');
    if (rs[u]) dfs(rs[u]);
}
int main()
{
    scanf("%d%d",&n,&m);
    root=Build(1,n+2);
    for (int i=1,l,r;i<=m;i++)
    l=read(),r=read(),rev(l+1,r+1);
    dfs(root);
    return 0;
}