[线段树合并]

推荐黄嘉泰的线段树合并

HNOI永无乡

#include <stdio.h>
#define maxn 100010

int n, m, id[maxn];

struct Edge{int to, nxt;}edge[maxn << 1];
int h[maxn], cnt;
void add(int u, int v){
	edge[++ cnt] = (Edge){v, h[u]}; h[u] = cnt;
	edge[++ cnt] = (Edge){u, h[v]}; h[v] = cnt;
}

int root[maxn], val[maxn];
bool vis[maxn];

int fa[maxn];
int getfa(int x){return x == fa[x] ? x : fa[x] = getfa(fa[x]);}

#define TREE 5000010
int lc[TREE], rc[TREE], size[TREE], Size;

void insert(int& rt, int l, int r, int x){
	if(!rt)rt = ++ Size;
	size[rt] ++;
	if(l == r)return;
	int mid = l + r >> 1;
	if(x <= mid)insert(lc[rt], l, mid, x);
	else insert(rc[rt], mid+1, r, x);
}

int merge(int x, int y){
	if(x == 0 || y == 0)return x + y;
	lc[x] = merge(lc[x], lc[y]);
	rc[x] = merge(rc[x], rc[y]);
	size[x] = size[lc[x]] + size[rc[x]];
	return x;
}

int ask(int rt, int l, int r, int k){
	if(l == r)return id[l];
	int mid = l + r >> 1;
	if(k <= size[lc[rt]])
		return ask(lc[rt], l, mid, k);
	k -= size[lc[rt]];
	return ask(rc[rt], mid+1, r, k);
}

int main(){
	scanf("%d%d", &n, &m);
	static int w[maxn];
	for(int i = 1; i <= n; i ++)
	    scanf("%d", &val[i]), id[val[i]] = i;

	int u, v;
	for(int i = 1; i <= n; i ++)fa[i] = i;
	for(int i = 1; i <= m; i ++){
	    scanf("%d%d", &u, &v);
		u = getfa(u), v = getfa(v);
		fa[getfa(v)] = getfa(u);
	}
	
	for(int i = 1; i <= n; i ++)
		insert(root[getfa(i)], 1, n, val[i]);
	int test; char cmd[2];
	scanf("%d", &test);
	while(test --){
		scanf("%s", cmd);
		if(cmd[0] == 'Q'){
			scanf("%d%d", &u, &v), u = getfa(u);
			if(size[root[u]] < v){puts("-1");continue;}
			printf("%d\n", ask(root[u], 1, n, v));
		}
		else{
			scanf("%d%d", &u, &v);
			u = getfa(u), v = getfa(v);
			if(u == v)continue;
			root[u] = merge(root[u], root[v]);
			fa[getfa(v)] = getfa(u);
		}
	}
	return 0;
}

[BZOJ 3702]二叉树

#include <bits/stdc++.h>
#define maxn 400010
#define TREE 5000010
using namespace std;
 
int n, son[maxn][2], w[maxn], root[maxn];
int cnt;
int get_tree(){
    int x = ++ cnt, a;
    scanf("%d", &a);
    if(a)w[x] = a;
    else{
        son[x][0] = get_tree();
        son[x][1] = get_tree();
    }
    return x;
}
 
typedef long long ll;
ll sum1, sum2, ans, sz[TREE];
int lc[TREE], rc[TREE], tr_cnt;
 
int merge(int x, int y){
    if(x == 0 || y == 0)return x + y;
    sum1 += sz[lc[x]] * sz[rc[y]];
    sum2 += sz[lc[y]] * sz[rc[x]];
    lc[x] = merge(lc[x], lc[y]);
    rc[x] = merge(rc[x], rc[y]);
    sz[x] = sz[lc[x]] + sz[rc[x]];
    return x;
}
 
void insert(int &rt, int l, int r, int x){
    rt = ++ tr_cnt;
    sz[rt] = 1;
    if(l == r)return;
    int mid = l + r >> 1;
    if(x <= mid) insert(lc[rt], l, mid, x);
    else insert(rc[rt], mid+1, r, x);
}
 
void dfs(int x){
    if(son[x][0] && son[x][1]){
        dfs(son[x][0]); dfs(son[x][1]);
        sum1 = sum2 = 0;
        root[x] = merge(root[son[x][0]], root[son[x][1]]);
        ans += min(sum1, sum2);
    }
    else insert(root[x], 1, n, w[x]);
}
 
int main(){
    scanf("%d", &n);
    int root = get_tree();
    dfs(root);
    printf("%lld\n", ans);
    return 0;
}

[BZOJ 3307]雨天的尾巴

#include <bits/stdc++.h>
#define maxn 100010
using namespace std;

int n, m;

struct Edge{
	int to, nxt;
}edge[maxn << 1];
int h[maxn], cnt;
void add(int u, int v){
	edge[++ cnt] = (Edge){v, h[u]}; h[u] = cnt;
	edge[++ cnt] = (Edge){u, h[v]}; h[v] = cnt;
}

int anc[maxn][20], fa[maxn], dep[maxn];
vector<int> hav[maxn];

void dfs(int u){
	dep[u] = dep[fa[u]] + 1;
	for(int i = h[u]; i; i = edge[i].nxt){
		int v = edge[i].to;
		if(v == fa[u])continue;
		fa[v] = anc[v][0] = u;
		dfs(v);
	}
}

int ask_LCA(int p, int q){
	if(dep[p] < dep[q])swap(p, q);
	int log = 1;
	for(; 1 << log <= dep[p]; log ++);log --;
	for(int i = log; ~i; i --)
	    if(dep[anc[p][i]] >= dep[q])
	        p = anc[p][i];
	if(p == q)return p;
	for(int i = log; ~i; i --)
	    if(anc[p][i] != anc[q][i])
	        p = anc[p][i], q = anc[q][i];
	return fa[p];
}

int ans[maxn];
int p[maxn], c;//离散
#define M 5000010
int pos[M], lc[M], rc[M], mx[M], root[maxn], size;

void pushup(int o){
    if(mx[lc[o]] >= mx[rc[o]]){
		mx[o] = mx[lc[o]];
		pos[o] = pos[lc[o]];
	}
	else{
        mx[o] = mx[rc[o]];
		pos[o] = pos[rc[o]];
	}
}

void insert(int& o, int l, int r, int val, int w){
	if(o == 0){o = ++ size; pos[o] = l;}
	if(l == r){mx[o] += w;return;}
	int mid = l + r >> 1;
	if(val <= mid)insert(lc[o], l, mid, val, w);
	else insert(rc[o], mid+1, r, val, w);
	pushup(o);
}

int merge(int x, int y, int l, int r){
	if(x == 0 || y == 0)
	    return x + y;
	if(l == r){
		mx[x] += mx[y];
		pos[x] = l;
	}
	else{
		int mid = l + r >> 1;
        lc[x] = merge(lc[x], lc[y], l, mid);
		rc[x] = merge(rc[x], rc[y], mid+1, r);
		pushup(x);
	}return x;
}

void solve(int u){
	for(int i = h[u]; i; i = edge[i].nxt){
		int v = edge[i].to;
		if(v == fa[u])continue;
		solve(v);
		root[u] = merge(root[u], root[v], 1, c);
	}
	
	for(int i = 0; i < hav[u].size(); i ++){
		int nw = hav[u][i], flag = nw > 0 ? 1 : -1;
		nw = lower_bound(p + 1, p + 1 + c, abs(nw)) - p;
	    insert(root[u], 1, c, nw, flag);
	}
	
	ans[u] = mx[root[u]] > 0 ? p[pos[root[u]]] : 0;
}

int main(){
	scanf("%d%d", &n, &m);
	int u, v, w;
	for(int i = 1; i < n; i ++)
		scanf("%d%d", &u, &v), add(u, v);
	dfs(1);
	for(int j = 1; 1 << j <= n; j ++)
		for(int i = 1; i <= n; i ++)
		    anc[i][j] = anc[anc[i][j-1]][j-1];
	
	p[0] = 0;
	for(int i = 1; i <= m; i ++){
		scanf("%d%d%d", &u, &v, &w);
		int LCA = ask_LCA(u, v);
		hav[u].push_back(w);
		hav[v].push_back(w);
		hav[LCA].push_back(-w);
		if(LCA != 1)hav[fa[LCA]].push_back(-w);
		p[++ c] = w;
	}
	sort(p + 1, p + 1 + c);
	c = unique(p + 1, p + 1 + c) - p - 1;

	solve(1);
	for(int i = 1; i <= n; i ++)
	    printf("%d\n", ans[i]);
	return 0;
}