[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=;
 const int sizeOfEdge=;
 
 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<<];
 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=;i<=n;i++)
         w[i]=getint();
     for (int i=;i<n;i++)
     {
         int u=getint(), v=getint();
         link(u, v);
     }
 
     dfsTree();
     dfsChain();
     build();
 
     q=getint();
     for (int i=;i<=q;i++)
     {
         ch=getch(), u=getint(), v=getint();
 
         if (ch=='Q') putint(queryChain(u, v));
         else updateItem(idx[u], v);
     }
 
     return ;
 }
 inline char getch()
 {
     register char ch;
     do ch=getchar(); while (ch!='Q' && ch!='C');
     return ch;
 }
 inline int getint()
 {
     register int num=;
     register char ch;
     do ch=getchar(); while (ch<'' || ch>'');
     do num=num*+ch-'', ch=getchar(); while (ch>='' && ch<='');
     return num;
 }
 inline void putint(int num)
 {
     if (num>) putchar('Y'), putchar('e'), putchar('s');
     else putchar('N'), putchar('o');
     putchar('\n');
 }
 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[]=;
     s[]=;
     for (stack[++tot]=;tot; )
     {
         u=stack[tot];
 
         edge *& i=t[u];
         for ( ;i && d[i->point]>=;i=i->next);
         if (i)
         {
             stack[++tot]=i->point;
             f[i->point]=u;
             d[i->point]=d[u]+;
             s[i->point]=;
         }
         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[]=num=; top[]=;
     for (stack[++tot]=;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=;m<n+;m<<=);
     for (int i=;i<=n;i++) T[idx[i]+m]=w[i];
     for (int i=m;i>=;i--) T[i]=T[i<<]^T[i<<|];
 }
 inline void updateItem(int i, int t)
 {
     for (T[i+=m]=t, i>>=;i;i>>=) T[i]=T[i<<]^T[i<<|];
 }
 inline int querySegment(int l, int r)
 {
     int sum=;
     for (l=l+m-, r=r+m+;l^r^;l>>=, r>>=)
     {
         if (~l&) sum^=T[l^];
         if ( r&) sum^=T[r^];
     }
     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=;
     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;
 }

1A 好评如潮