【线段树 树链剖分 差分 经典技巧】loj#3046. 「ZJOI2019」语言【未完】

还是来致敬一下那过往吧

题目分析

先丢代码

 #include<bits/stdc++.h>
 const int maxn = ;
 const int maxm = ;
 const int maxNode = ;

 struct node
 {
     int top,son,fa,tot;
 }a[maxn];
 struct point
 {
     int u,v;
     point(int a=, int b=):u(a),v(b) {}
 };
 struct tree
 {
     int ls,rs,cov,val;
 }f[maxNode];
 int n,m,tot;
 long long ans,det;
 int chain[maxn],chTot,rt[maxn];
 int edgeTot,head[maxn],edges[maxm],nxt[maxm],dep[maxn];
 std::vector<point> opt[maxn];
 std::vector<int> inc[maxn],dec[maxn];

 int read()
 {
     char ch = getchar();
     int num = , fl = ;
     for (; !isdigit(ch); ch=getchar())
         if (ch=='-') fl = -;
     for (; isdigit(ch); ch=getchar())
         num = (num<<)+(num<<)+ch-;
     return num*fl;
 }
 void addedge(int u, int v)
 {
     edges[++edgeTot] = v, nxt[edgeTot] = head[u], head[u] = edgeTot;
     edges[++edgeTot] = u, nxt[edgeTot] = head[v], head[v] = edgeTot;
 }
 void dfs1(int x, int fa)
 {
     dep[x] = dep[fa]+, a[x].tot = ;
     a[x].top = a[x].son = -, a[x].fa = fa;
     for (int i=head[x]; i!=-; i=nxt[i])
     {
         int v = edges[i];
         if (v==fa) continue;
         dfs1(v, x), a[x].tot += a[v].tot;
         if (a[x].son==-||a[a[x].son].tot < a[v].tot)
             a[x].son = v;
     }
 }
 void dfs2(int x, int top)
 {
     a[x].top = top, chain[x] = ++chTot;
     if (a[x].son==-) return;
     dfs2(a[x].son, top);
     for (int i=head[x]; i!=-; i=nxt[i])
         if (edges[i]!=a[x].fa&&edges[i]!=a[x].son)
             dfs2(edges[i], edges[i]);
 }
 void splitChain(int id, int u, int v)
 {
     inc[u].push_back(id), inc[v].push_back(id);
     while (a[u].top!=a[v].top)
     {
         if (dep[a[u].top] > dep[a[v].top]) std::swap(u, v);
         opt[id].push_back(point(chain[a[v].top], chain[v]));
         v = a[a[v].top].fa;
     }
     if (dep[u] > dep[v]) std::swap(u, v);
     opt[id].push_back(point(chain[u], chain[v]));
     dec[u].push_back(id), dec[a[u].fa].push_back(id);
 }
 void pushup(int rt, int len)
 {
     if (f[rt].cov) f[rt].val = len;
     else f[rt].val = f[f[rt].ls].val+f[f[rt].rs].val;
 }
 void mergeSeg(int &u, int v, int l, int r)
 {
     if (!u||!v) u += v;
     else{
         int mid = (l+r)>>;
         f[u].cov += f[v].cov;
         mergeSeg(f[u].ls, f[v].ls, l, mid);
         mergeSeg(f[u].rs, f[v].rs, mid+, r);
     }
     pushup(u, r-l+);
 }
 void update(int &rt, int L, int R, int l, int r, int c)
 {
     if (!rt) rt = ++tot;
     if (L <= l&&r <= R) f[rt].cov += c, pushup(rt, r-l+);
     else{
         int mid = (l+r)>>;
         if (L <= mid) update(f[rt].ls, L, R, l, mid, c);
         if (R > mid) update(f[rt].rs, L, R, mid+, r, c);
     }
     pushup(rt, r-l+);
 }
 void delta(int x, int fa)
 {
     for (int i=head[x]; i!=-; i=nxt[i])
         if (edges[i]!=fa) delta(edges[i], x);
     for (int l=; l<inc[x].size(); l++)
         for (int i=,mx=opt[inc[x][l]].size(); i<mx; i++)
             update(rt[x], opt[inc[x][l]][i].u, opt[inc[x][l]][i].v, , n, );
     for (int l=; l<dec[x].size(); l++)
         for (int i=,mx=opt[dec[x][l]].size(); i<mx; i++)
             update(rt[x], opt[dec[x][l]][i].u, opt[dec[x][l]][i].v, , n, -);
     int val = f[rt[x]].val;
     if (val) ans += val, ++det;
     mergeSeg(rt[fa], rt[x], , n);
 }
 int main()
 {
     memset(head, -, sizeof head);
     n = read(), m = read();
     for (int i=; i<n; i++)
         addedge(read(), read());
     dfs1(, ), dfs2(, );
     for (int i=; i<=m; i++)
         splitChain(i, read(), read());
     delta(, );
     printf("%lld\n",(ans-det)/);
     return ;
 }