loj#2054. 「TJOI / HEOI2016」树

题目链接

loj#2054. 「TJOI / HEOI2016」树

题解

每次标记覆盖整棵字数，子树维护对于标记深度取max
dfs序+线段树维护一下

代码

#include<cstdio> 
#include<algorithm> 

inline int read() {
	int x = 0,f = 1; 
	char c = getchar(); 
	while(c < '0' || c > '9')c = getchar(); 
	while(c <= '9' && c >= '0') x = x * 10 + c - '0',c = getchar(); 
	return x * f; 
} 
int n,m; 
const int maxn = 200007; 
struct node {
	int v,next; 
} edge[maxn << 1]; 
int head[maxn],num = 0; 
inline void add_edge(int u,int v) { 
	edge[++ num].v = v; edge[num].next = head[u];head[u] = num; 
	edge[++ num].v = u; edge[num].next = head[v];head[v] = num; 
} 

int dfn[maxn],low[maxn],dep[maxn]; 
struct seg { 
#define ls x << 1,l,mid
#define rs x << 1 | 1,mid + 1,r
	int t[maxn << 1]; 
	void build(int x,int l,int r) { 
		if(l == r) { t[x] = 1; return; }  
		int mid = l + r >> 1; 
		build(ls); 
		build(rs); 
 	} 
	inline void cover(int x,int k) { 
 		if(!t[x]) t[x] = k; 
		else  t[x] = dep[t[x]] < dep[k] ? k : t[x]; 
	 } 
	inline void pushdown(int x) {
	 	cover(x << 1,t[x]); 
	 	cover(x << 1 | 1,t[x]); 
	 	t[x] = 0; 
	} 
	int query(int x,int l,int r,int k) {
		if(l == r)  return t[x]; 
		if(t[x]) pushdown(x); 
		int mid = l + r >> 1; 
		if(k <= mid) return query(ls,k); 
		else return query(rs,k); 
	} 
 	void modify(int x,int l,int r,int L,int R,int k) { 
 		if(L <= l && R >= r) { 
 			cover(x,k); return ; 
 		} 
 		if(t[x]) pushdown(x); 
 		int mid = l + r >> 1; 
		if(L <= mid) modify(ls,L,R,k); 
		if(R > mid ) modify(rs,L,R,k);  
	} 
}t;  

int idx = 0; 
void dfs(int x,int fa = 0) { 
	dfn[x] =++ idx; 
	dep[x] = dep[fa] + 1; 
	for(int i = head[x];i;i = edge[i].next) 
		if(edge[i].v != fa) dfs(edge[i].v,x); 
	low[x] = idx; 
} 
int main() { 
	n = read(); m = read(); 
	int cnt = 1; 
	for(int i = 1;i < n;++ i) { 
		add_edge(read(),read()); 
	} 
	dfs(1); 
	t.build(1,1,n); 
	char ty[3]; 
	for(int x,i = 1;i <= m;i += 1) {
		scanf("%s",ty + 1); 
		if(ty[1] == 'Q') {
			printf("%d\n",t.query(1,1,n,dfn[read()])); 
		} else { 
			x = read(); 
			t.modify(1,1,n,dfn[x],low[x],x); 
		} 
	} 
	return 0; 
}