P3806 【模板】点分治1

一道淀粉质的模版题，开始是暴力

 #include <bits/stdc++.h>
 #define up(i,l,r) for(register int i = (l); i <= (r); ++i)
 #define dn(i,l,r) for(register int i = (l); i >= (r); --i)
 #define ll long long
 #define re register
 using namespace std;

 template <typename T> void in(T &x) {
     x = ; T f = ; char ch = getchar();
     while(!isdigit(ch)) {if(ch == '-') f = -; ch = getchar();}
     while( isdigit(ch)) {x =  * x + ch - ; ch = getchar();}
     x *= f;
 }

 template <typename T> void out(T x) {
     if(x < ) x = -x , putchar('-');
     if(x > ) out(x/);
     putchar(x% + );
 }
 //---------------------------------------------------------

 const int N = ;

 int n,m;

 struct edge {
     int v,w,nxt;
 }e[N<<]; int tot,head[N];

 void add(int u,int v,int w) {
     e[++tot].v = v; e[tot].w = w; e[tot].nxt = head[u]; head[u] = tot;
 }

 int Tsize,f[N],rt;
 int size[N];
 bool vis[N];

 void get_rt(int u,int fa) {
     size[u] = ; f[u] = ;
     for(re int i = head[u];i ;i = e[i].nxt) {
         int v = e[i].v; if(v == fa || vis[v]) continue;
         get_rt(v,u);
         size[u] += size[v]; f[u] = max(f[u],size[v]);
     }
     f[u] = max(f[u],Tsize - size[u]);
     if(f[u] < f[rt]) rt = u;
 }

 int dis[N],cdis[N];
 int ans[];
 int cnt;

 void get_dis(int u,int fa) {
     cdis[++cnt] = dis[u];
     for(re int i = head[u]; i; i = e[i].nxt) {
         int v = e[i].v; if(v == fa || vis[v]) continue;
         dis[v] = dis[u] + e[i].w; get_dis(v,u);
     }
 }

 void calc(int u,int w) {
     cnt = ; get_dis(u,);
     up(i,,cnt) {
         up(j,,cnt) {
             if(i != j)
             ans[cdis[i] + cdis[j]] += w;
         }
     }
 }

 void solve(int u) {
     vis[u] = ; dis[u] = ; calc(u,);
     for(re int i = head[u]; i; i = e[i].nxt) {
         int v = e[i].v; if(vis[v]) continue;
         dis[v] = e[i].w; calc(v,-);
         Tsize = size[v]; rt = ;
         get_rt(v,); solve(rt);
     }
 }

 int main() {
     in(n); in(m); int x,y,w;
     up(i,,n-) {
         in(x); in(y); in(w);
         add(x,y,w); add(y,x,w);
     }
     Tsize = n,f[] = n+,rt = ;
     get_rt(,); solve(rt);
     int k;
     up(i,,m) {
         in(k);
         if(ans[k]) printf("AYE\n");
         else printf("NAY\n");
     }
     return ;
 }

然后我用了二分

 #include <bits/stdc++.h>
 #define up(i,l,r) for(register int i = (l); i <= (r); ++i)
 #define dn(i,l,r) for(register int i = (l); i >= (r); --i)
 #define ll long long
 #define re register
 using namespace std;

 template <typename T> void in(T &x) {
     x = ; T f = ; char ch = getchar();
     while(!isdigit(ch)) {if(ch == '-') f = -; ch = getchar();}
     while( isdigit(ch)) {x =  * x + ch - ; ch = getchar();}
     x *= f;
 }

 template <typename T> void out(T x) {
     if(x < ) x = -x , putchar('-');
     if(x > ) out(x/);
     putchar(x% + );
 }
 //---------------------------------------------------------

 const int N = ;

 int n,m;

 struct edge {
     int v,w,nxt;
 }e[N<<]; int tot,head[N];

 void add(int u,int v,int w) {
     e[++tot].v = v; e[tot].w = w; e[tot].nxt = head[u]; head[u] = tot;
 }

 int Tsize,f[N],rt;
 int size[N];
 bool vis[N];

 void get_rt(int u,int fa) {
     size[u] = ; f[u] = ;
     for(re int i = head[u];i ;i = e[i].nxt) {
         int v = e[i].v; if(v == fa || vis[v]) continue;
         get_rt(v,u);
         size[u] += size[v]; f[u] = max(f[u],size[v]);
     }
     f[u] = max(f[u],Tsize - size[u]);
     if(f[u] < f[rt]) rt = u;
 }

 int dis[N];
 int cnt;
 int belong;

 struct cur {
     int dis,bl;
     bool operator < (const cur &x) const {
         return dis < x.dis;
     }
 }c[N];

 void get_dis(int u,int fa) {
     c[++cnt] = (cur){dis[u],belong};
     for(re int i = head[u]; i; i = e[i].nxt) {
         int v = e[i].v; if(v == fa || vis[v]) continue;
         dis[v] = dis[u] + e[i].w; get_dis(v,u);
     }
 }

 int binary(int x) {
     int l = ,r = cnt; int res = ;
     while(l <= r) {
         int mid = (l+r)>>;
         if(x <= c[mid].dis) res = mid,r = mid - ;
         else l = mid + ;
     }
     return res;
 }

 bool test[];
 int flag;
 int k[];

 void calc(int u) {
     cnt = ;

     for(re int i = head[u];i;i = e[i].nxt) {
         int v = e[i].v; if(vis[v]) continue;
         dis[v] = e[i].w; belong = v; get_dis(v,u);
     }

     c[++cnt] = (cur){,};//自己也算一个; 

     sort(c+,c+cnt+);

     up(i,,m) {
         up(j,,cnt) {
             if(flag == ) return;
             if(test[i]) break;
             int r = binary(k[i]-c[j].dis);
             if(c[j].bl != c[r].bl && c[j].dis + c[r].dis == k[i]) {
                 test[i] = ; flag -= i; break;
             }
         }
     }
 }

 void solve(int u) {
     if(flag == ) return;
     vis[u] = ; dis[u] = ;
     calc(u);
     for(re int i = head[u]; i; i = e[i].nxt) {
         int v = e[i].v; if(vis[v]) continue;
         Tsize = size[v]; rt = ;
         get_rt(v,); solve(rt);
     }
 }

 int main() {
     in(n); in(m); int x,y,w;

     up(i,,n-) {
         in(x); in(y); in(w);
         add(x,y,w); add(y,x,w);
     }
     up(i,,m) in(k[i]);

     flag = (m*(m+))/;

     Tsize = n,f[] = n+,rt = ;
     get_rt(,); solve(rt);

     up(i,,m) {
         if(test[i]) printf("AYE\n");
         else printf("NAY\n");
     }

     return ;
 }

虽然还可以更快，但我不想打了