BZOJ 2631 Tree ——Link-Cut Tree

【题目分析】

又一道LCT的题目，LCT只能维护链上的信息。

【代码】

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>

#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <vector>
#include <iostream>
#include <queue>

using namespace std;

#define maxn 1000005
#define inf (0x3f3f3f3f)
#define mod 51061

unsigned int read()
{
    unsigned int x=0,f=1; char ch=getchar();
    while (ch<'0'||ch>'9') {if (ch=='-') f=-1; ch=getchar();}
    while (ch>='0'&&ch<='9') {x=x*10+ch-'0'; ch=getchar();}
    return x*f;
}

unsigned int ch[maxn][2],fa[maxn],add[maxn],mul[maxn],num[maxn],sum[maxn];
unsigned int n,m,siz[maxn],rev[maxn],sta[maxn],top=0;

void update(unsigned int x)
{
    siz[x]=siz[ch[x][0]]+siz[ch[x][1]]+1;
    sum[x]=(sum[ch[x][0]]+sum[ch[x][1]]+num[x])%mod;
}

void solve(unsigned int x,unsigned int ad,unsigned int ml)
{
    if (!x) return ;
    add[x]=(add[x]*ml+ad)%mod; mul[x]=(mul[x]*ml)%mod;
    sum[x]=(sum[x]*ml+siz[x]*ad)%mod; num[x]=(num[x]*ml+ad)%mod;
}

void pushdown(unsigned int x)
{
    if (rev[x])
    {
        rev[x]^=1;
        rev[ch[x][0]]^=1;
        rev[ch[x][1]]^=1;
        swap(ch[x][0],ch[x][1]);
    }
    solve(ch[x][0],add[x],mul[x]);
    solve(ch[x][1],add[x],mul[x]);
    mul[x]=1; add[x]=0;
}

bool isroot(unsigned int x)
{
    return ch[fa[x]][0]!=x&&ch[fa[x]][1]!=x;
}

void rot(unsigned int x)
{
    unsigned int y=fa[x],z=fa[y],l,r;
    if (ch[y][0]==x) l=0; else l=1;
    r=l^1;
    if (!isroot(y))
    {
        if (ch[z][0]==y) ch[z][0]=x;
        else ch[z][1]=x;
    }
    fa[x]=z; fa[y]=x; fa[ch[x][r]]=y;
    ch[y][l]=ch[x][r]; ch[x][r]=y;
    update(y); update(x);
}

void splay(unsigned int x)
{
    unsigned int top=0; sta[top++]=x;
    for (int i=x;!isroot(i);i=fa[i]) sta[top++]=fa[i];
    while (top--) pushdown(sta[top]);

    while (!isroot(x))
    {
        unsigned int y=fa[x],z=fa[y];
        if (!isroot(y))
        {
            if (ch[z][0]==y^ch[y][0]==x) rot(x);
            else rot(y);
        }
        rot(x);
    }
}

void access(unsigned int x)
{
    for (int t=0;x;t=x,x=fa[x])
        splay(x),ch[x][1]=t,update(x);
}

void makeroot(unsigned int x)
{
    access(x);
    splay(x);
    rev[x]^=1;
}

unsigned int find(unsigned int x)
{
    access(x);
    splay(x);
    while (ch[x][0]) x=ch[x][0];
    return x;
}

void link(unsigned int x,unsigned int y)
{
    makeroot(x);
    fa[x]=y;
}

void cut(unsigned int x,unsigned int y)
{
    makeroot(x);
    access(y);
    splay(y);
    ch[y][0]=fa[x]=0;
}

int main()
{
    n=read();m=read();
    for (unsigned int i=1;i<=n;++i) num[i]=1,update(i);
    char opt[10];
    for (unsigned int i=1;i<n;++i) link(read(),read());
    while (m--)
    {
        scanf("%s",opt);
        unsigned int x,y,z;
        switch (opt[0])
        {
            case '+':
                x=read(); y=read(); z=read();
                makeroot(x);
                access(y);
                splay(y);
                solve(y,z,1);
                break;
            case '-':
                cut(read(),read()); link(read(),read());
                break;
            case '*':
                x=read();y=read();z=read();
                makeroot(x);
                access(y);
                splay(y);
                solve(y,0,z);
                break;
            case '/':
                x=read();y=read();
                makeroot(x);
                access(y);
                splay(y);
                printf("%u\n",sum[y]);
                break;
        }
    }
}