[BZOJ 2819]Nim

最近都忙的没空写题解了喵～

看到 1= 终于是保住了也算是一个小小的安慰吧 555……

湖北省队互测题，据说会爆栈，但 Linux 下 栈空间=内存=128M 真的吃不下？

反正我是写了个人工栈～

这似乎是我近 4 天里写的第 3 道树链剖分？

#include <cstdio>
#include <cstring>
#include <cstdlib>
const int sizeOfPoint=500005;
const int sizeOfEdge=1000001;

int n, m, q;
int w[sizeOfPoint];
int f[sizeOfPoint], d[sizeOfPoint], s[sizeOfPoint];
int num, idx[sizeOfPoint], top[sizeOfPoint], son[sizeOfPoint];
inline char getch();
inline int getint();
inline void putint(int);

struct edge {int point; edge * next;};
edge memory[sizeOfEdge], * port=memory;
edge * e[sizeOfPoint];
inline edge * newedge(int, edge * );
inline void link(int, int);

int tot, stack[sizeOfPoint];
edge * t[sizeOfPoint];
inline void dfsTree();
inline void dfsChain();

int T[sizeOfPoint<<2];
inline void build();
inline void updateItem(int, int);
inline int querySegment(int, int);

inline void swap(int & , int & );
inline int queryChain(int, int);

int main()
{
    char ch;
    int u, v;

    n=getint();
    for (int i=1;i<=n;i++)
        w[i]=getint();
    for (int i=1;i<n;i++)
    {
        int u=getint(), v=getint();
        link(u, v);
    }

    dfsTree();
    dfsChain();
    build();

    q=getint();
    for (int i=1;i<=q;i++)
    {
        ch=getch(), u=getint(), v=getint();

        if (ch=='Q') putint(queryChain(u, v));
        else updateItem(idx[u], v);
    }

    return 0;
}
inline char getch()
{
    register char ch;
    do ch=getchar(); while (ch!='Q' && ch!='C');
    return ch;
}
inline int getint()
{
    register int num=0;
    register char ch;
    do ch=getchar(); while (ch<'0' || ch>'9');
    do num=num*10+ch-'0', ch=getchar(); while (ch>='0' && ch<='9');
    return num;
}
inline void putint(int num)
{
    if (num>0) putchar('Y'), putchar('e'), putchar('s');
    else putchar('N'), putchar('o');
    putchar('
');
}
inline edge * newedge(int point, edge * next)
{
    edge * ret=port++;
    ret->point=point; ret->next=next;
    return ret;
}
inline void link(int u, int v)
{
    e[u]=newedge(v, e[u]); e[v]=newedge(u, e[v]);
}
inline void dfsTree()
{
    int u;

    memcpy(t, e, sizeof(e));
    memset(d, 0xFF, sizeof(d)); d[1]=0;
    s[1]=1;
    for (stack[++tot]=1;tot; )
    {
        u=stack[tot];

        edge *& i=t[u];
        for ( ;i && d[i->point]>=0;i=i->next);
        if (i)
        {
            stack[++tot]=i->point;
            f[i->point]=u;
            d[i->point]=d[u]+1;
            s[i->point]=1;
        }
        else
        {
            if (!f[u]) break;
            s[f[u]]+=s[u];
            if (s[u]>s[son[f[u]]])
                son[f[u]]=u;
            tot--;
        }
    }
}
inline void dfsChain()
{
    int u;

    memcpy(t, e, sizeof(e));
    idx[1]=num=1; top[1]=1;
    for (stack[++tot]=1;tot; )
    {
        u=stack[tot];
        if (son[u] && !idx[son[u]])
        {
            stack[++tot]=son[u];
            idx[son[u]]=++num;
            top[son[u]]=top[u];
            continue;
        }

        edge *& i=t[u];
        for ( ;i && idx[i->point];i=i->next);
        if (i)
        {
            stack[++tot]=i->point;
            idx[i->point]=++num;
            top[i->point]=i->point;
        }
        else
        {
            if (!f[u]) break;
            tot--;
        }
    }
}
inline void build()
{
    for (m=1;m<n+2;m<<=1);
    for (int i=1;i<=n;i++) T[idx[i]+m]=w[i];
    for (int i=m;i>=1;i--) T[i]=T[i<<1]^T[i<<1|1];
}
inline void updateItem(int i, int t)
{
    for (T[i+=m]=t, i>>=1;i;i>>=1) T[i]=T[i<<1]^T[i<<1|1];
}
inline int querySegment(int l, int r)
{
    int sum=0;
    for (l=l+m-1, r=r+m+1;l^r^1;l>>=1, r>>=1)
    {
        if (~l&1) sum^=T[l^1];
        if ( r&1) sum^=T[r^1];
    }
    return sum;
}
inline void swap(int & u, int & v)
{
    int t=u; u=v; v=t;
}
inline int queryChain(int u, int v)
{
    int sum=0;
    while (top[u]!=top[v])
    {
        if (d[top[u]]<d[top[v]]) swap(u, v);
        sum^=querySegment(idx[top[u]], idx[u]);
        u=f[top[u]];
    }
    if (d[u]>d[v]) swap(u, v);
    sum^=querySegment(idx[u], idx[v]);
    return sum;
}