bzoj3545: [ONTAK2010]Peaks 重构树 主席树

题目链接

bzoj3545: [ONTAK2010]Peaks

题解

套路重构树上主席树

代码

#include<cstdio>
#include<algorithm>
#define gc getchar
#define pc putchar
inline int read() {
	int x = 0,f = 1;
	char c = getchar();
	while(c < '0' || c > '9') { if(c == '-')f = -1; c = gc(); }
	while(c <= '9' && c >= '0') x = x * 10 + c - '0',c = gc();
	return x * f;
}
void print(int x) {
	if(x < 0) {
		pc('-');
		x = -x;
	}
	if(x >= 10) print(x / 10);
	pc(x % 10 + '0');
}
int n,m,q;
const int maxn = 500007;
int h[maxn];
struct node {
	int u,v,w,next;
} e[maxn],edge[maxn];
int num = 0,head[maxn];
inline void add_edge(int u,int v) {
	edge[++ num].v = v; edge[num].next = head[u],head[u] = num;
}
inline bool cmp(node a,node b) {
	return a.w < b.w;
}
int fa[maxn];
int dad[maxn][23],mn[maxn];
int tot = 0;
int L[maxn],R[maxn];
int rt[maxn];
int lin[maxn],cnt = 0;
void dfs(int x) {
	L[x] = 0x3f3f3f3f;
	R[x] = 0;
	if(!head[x]) {
		lin[++ cnt] = x;
		L[x] = R[x] = cnt;
		return;
	}
	for(int i = head[x];i ;i = edge[i].next) {
		int v = edge[i].v;
		dfs(v);
		L[x] = std::min(L[v],L[x]);
		R[x] = std::max(R[v],R[x]);
	}
} 

int b[maxn];
int sum = 0;
struct Cmt {
	int ls[100000 * 20],rs[100000 * 20],siz[100000 * 20];
	void insert(int px,int &x,int l,int r,int k) {
		x = ++ sum;
		siz[x] = siz[px] + 1;
		if(l == r) return;
		ls[x] = ls[px], rs[x] = rs[px];
		int mid = l + r >> 1;
		if(k <= mid) insert(ls[px],ls[x],l,mid,k);
		else insert(rs[px],rs[x],mid + 1,r,k);
	}
	int query(int lx,int rx,int l,int r,int k) {
		if(l == r) return l;
		int mid = l + r >> 1, tmp = siz[rs[rx]] - siz[rs[lx]];
		if(tmp >= k) return query(rs[lx],rs[rx],mid + 1,r,k);
		else return query(ls[lx],ls[rx],l,mid,k - tmp);
	}
} t;
int get(int x,int val) {
	for(int i = 20;i >= 0;-- i)
		if(mn[dad[x][i]] <= val)
		x = dad[x][i];
	return x;
}
int find(int x) {
	if(fa[x] != x) fa[x] = find(fa[x]);
	return fa[x];
}
int main() {
	mn[0] = 0x3f3f3f3f;
	n = read(); m = read(); q = read();
	for(int i = 1;i <= n;++ i) b[i] = h[i] = read();
	std::sort(b + 1,b + n + 1);
	int len = std::unique(b + 1,b + n + 1) - b - 1; 

	for(int i = 1;i <= n;++ i) h[i] = std::lower_bound(b + 1,b + len + 1,h[i]) - b; 

	for(int i = 1;i <= m;++ i)
		e[i].u = read(),e[i].v = read(),e[i].w = read();
	tot = n;
	for(int i = 1;i <= n;++ i) fa[i] = i;
	std::sort(e + 1,e + m + 1,cmp);
	int nnn = 0;
	for(int i = 1;i <= m;++ i) {
		int u = e[i].u,v = e[i].v;
		int fu = find(u),fv = find(v);
		if(fu != fv) {
			++ tot;
			dad[fu][0] = tot;
			dad[fv][0] = tot;
			add_edge(tot,fu);
			add_edge(tot,fv);
			fa[fu] = tot;
			fa[fv] = tot;
			fa[tot] = tot;
			mn[tot] = e[i].w;
			nnn ++;
		}
		if(nnn == n - 1) break;
	}
	for(int i = 1;i <= 20;++ i)
		for(int j = 1;j <= tot; ++ j)
			dad[j][i] = dad[dad[j][i - 1]][i - 1];
	//print(dad[15][0]);
	dfs(tot);
	for(int i = 1;i <= cnt;++ i)
		t.insert(rt[i - 1],rt[i],1,len,h[lin[i]]);
	for(int i = 1;i <= q;++ i) {
		int v = read(),x = read(),k = read();
		int p = v;
		v = get(v,x);
		if(R[v] - L[v] + 1 < k) puts("-1");
		else print(b[t.query(rt[L[v] - 1],rt[R[v]],1,len,k)]),pc('\n');
	}
	return 0;
}
/*

*/