Construction of bzoj3572 _ virtual tree + lca and bzoj3572 construction of lca

Construction of bzoj3572 _ virtual tree + lca and bzoj3572 construction of lca

World Tree... frozen throne is certainly not a temporary agenda.

I have tried a variety of methods to find things related to the virtual tree. Finally, I understood this question with the help of the big God and DG. Although the gods do not say anything about the virtual tree, I will introduce the application of this question here. (Of course, some great gods do not know what virtual trees are)

For m points of each query, connect them on the original tree to form a subgraph, and add the lca of the m points to the subgraph, if you contract a vertex that is not a query vertex but a vertex whose degree is 2, a virtual tree corresponding to the current query is obtained. (I don't need to care about this name. I just re-constructed a graph)

At this time, we will find that the nodes at both ends of each edge in the virtual tree have their own ownership (this is a nonsense), so we will discuss the attribution of points on this chain, finally, the answer is displayed.

For the process of creating a virtual tree, see the code ...... I also summarized the code at the time. In short, I used the stack to maintain the rightmost link. Every time I updated the elements that were not added and the elements and the stack top, I would just do that.

Ps: it makes sense to see strange variable names.

#include <cstdio>#include <cstring>#include <algorithm>#include <queue>#define N 300000 + 10#define H 20#define INF 1000000000using namespace std;struct node{    int dist, bel;    node() { }    node(int x, int y)    {        dist = x;        bel = y;    }}g[N];struct edge{    int to, next;}e[2*N];int n, m, q, num, top, ind, cont, p[N], flag[N];int fa[N][H], fa_v[N], r[N], d[N], h[N], s[N], st[N];int sum[N], dfn[N], ans[N], val[N], delta[N];inline bool cmp(int x, int y){ return dfn[x] < dfn[y]; }node min(node a, node b){    if (a.dist == b.dist) return a.bel < b.bel ? a : b;    return a.dist < b.dist ? a : b;}void read(int &x){    x = 0;    char c = getchar();    while(c < '0' || c > '9') c = getchar();    while(c >= '0' && c <= '9')    {        x = 10*x + c - '0';        c = getchar();    }}void add(int x, int y){    e[++num].to = y;    e[num].next = p[x];    p[x] = num;}void init(){    int x, y;    read(n);    for (int i = 1; i < n; ++i)    {        read(x), read(y);        add(x, y);        add(y, x);    }}void bfs(){    queue<int>q;    q.push(1);    fa[1][0] = 1;    flag[1] = 1;    while(!q.empty())    {        int x = q.front();        q.pop();        for (int i = 1; i < H; ++i)        fa[x][i] = fa[fa[x][i-1]][i-1];        for (int i = p[x]; i; i = e[i].next)        {            int k = e[i].to;            if (!flag[k])            {                d[k] = d[x] + 1;                fa[k][0] = x;                flag[k] = 1;                q.push(k);            }        }    }}void dfs(int x){    sum[x] = 1;    dfn[x] = ++ind;    for (int i = p[x]; i; i = e[i].next)    {        int k = e[i].to;        if (k != fa[x][0])        {            dfs(k);            sum[x] += sum[k];        }    }}int lca(int x, int y){    if (d[x] > d[y]) swap(x, y);    int l = x, r = y;    for (int mid = d[r] - d[l], i = 0; mid; ++i, mid >>= 1)    if (mid & 1) r = fa[r][i];    if (l == r) return r;    for (int i = H - 1; i >= 0; i--)    {        if (fa[l][i] == fa[r][i]) continue;        l = fa[l][i], r = fa[r][i];    }    return fa[r][0];}int find(int x, int h){    for (int i = H - 1; i >= 0; i--)    if (d[fa[x][i]] >= h) x = fa[x][i];    return x;}void solve(){    top = cont = 0;    read(m);    for (int i = 1; i <= m; ++i)    {        read(h[i]);        s[++cont] = r[i] = h[i];        g[h[i]] = node(0, h[i]);        ans[h[i]] = 0;    }    sort(h+1, h+m+1, cmp);    for (int i = 1; i <= m; ++i)    {        int x = h[i];        if (!top)        {            st[++top] = x;            fa_v[x] = 0;        }        else        {            int anc = lca(x, st[top]);            while(d[st[top]] > d[anc])            {                if (d[st[top-1]] <= d[anc])                fa_v[st[top]] = anc;                top--;            }            if (st[top] != anc)            {                s[++cont] = anc;                g[anc] = node(INF, 0);                fa_v[anc] = st[top];                st[++top] = anc;            }            fa_v[x] = anc;            st[++top] = x;        }    }    sort(s+1, s+cont+1, cmp);    for (int i = 1; i <= cont; ++i)    {        int x = s[i];        val[x] = sum[x];        if (i > 1) delta[x] = d[x] - d[fa_v[x]];    }    for (int i = cont; i > 1; i--)    {        int x = s[i];        g[fa_v[x]] = min(g[fa_v[x]], node(g[x].dist+delta[x], g[x].bel));    }    for (int i = 2; i <= cont; ++i)    {        int x = s[i];        g[x] = min(g[x], node(g[fa_v[x]].dist+delta[x], g[fa_v[x]].bel));    }    for (int i = 1; i <= cont; ++i)    {        int x = s[i], anc = fa_v[x];        if (i == 1) ans[g[x].bel] += n - sum[x];        else        {            int k = find(x, d[anc]+1);            int del = sum[k] - sum[x];            val[anc] -= sum[k];            if (g[anc].bel == g[x].bel) ans[g[x].bel] += del;            else            {                int mid = d[x] - ((g[x].dist+g[fa_v[x]].dist+delta[x])/2-g[x].dist);                if ((g[x].dist+g[fa_v[x]].dist+delta[x]) % 2 == 0 && g[x].bel > g[fa_v[x]].bel) ++mid;                int tmp = sum[find(x, mid)] - sum[x];                ans[g[x].bel] += tmp;                ans[g[fa_v[x]].bel] += del - tmp;            }        }    }    for (int i = 1; i <= cont; ++i)    ans[g[s[i]].bel] += val[s[i]];    for (int i = 1; i <= m; ++i)    printf("%d ", ans[r[i]]);    putchar('\n');}void deal(){    bfs();    dfs(1);    read(q);    while(q--) solve();}int main(){    init();    deal();    return 0;}