【树链剖分】 POJ 3237 Tree

不难的树链剖分。。。用线段树维护最大值最小值即可。。。。

#include <iostream>
#include <queue> 
#include <stack> 
#include <map> 
#include <set> 
#include <bitset> 
#include <cstdio> 
#include <algorithm> 
#include <cstring> 
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 2000005
#define maxm 4000005
#define eps 1e-10
#define mod 1000000007
#define INF 1e9
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid 
#define rson o<<1 | 1, mid+1, R
//#pragma comment(linker, "/STACK:16777216")
typedef long long LL;
typedef unsigned long long ULL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}
LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}
// head

int mark[maxn << 2];
int maxv[maxn << 2];
int minv[maxn << 2];
int size[maxn];
int son[maxn];
int dep[maxn];
int top[maxn];
int fa[maxn];
int w[maxn];
char ss[maxn];
int n, z;

struct Edge
{
	int v;
	Edge *next;
}pool[maxm], *H[maxn], *edges;

struct node
{
	int u, v, c;
	node(int u = 0, int v = 0, int c = 0) : u(u), v(v), c(c) {}
}edge[maxn];

void init(void)
{
	z = 0;
	edges = pool;
	memset(H, 0, sizeof H);
}

void addedges(int u, int v)
{
	edges->v = v;
	edges->next = H[u];
	H[u] = edges++;
}

void read(void)
{
	int u, v, c;
	scanf("%d", &n);
	for(int i = 1; i < n; i++) {
		scanf("%d%d%d", &u, &v, &c);
		edge[i] = node(u, v, c);
		addedges(u, v);
		addedges(v, u);
	}
}

void dfs1(int u)
{
	size[u] = 1, son[u] = 0;
	for(Edge *e = H[u]; e; e = e->next) {
		int v = e->v;
		if(v != fa[u]) {
			dep[v] = dep[u] + 1;
			fa[v] = u;
			dfs1(v);
			size[u] += size[v];
			if(size[son[u]] < size[v]) son[u] = v;
		}
	}
}

void dfs2(int u, int tp)
{
	w[u] = ++z, top[u] = tp;
	if(son[u]) dfs2(son[u], tp);
	for(Edge *e = H[u]; e; e = e->next) {
		int v = e->v;
		if(v != fa[u] && v != son[u]) dfs2(v, v);
	}
}

void build(int o, int L, int R)
{
	maxv[o] = -INF, minv[o] = INF, mark[o] = 0;
	if(L == R) return;
	int mid = (L + R) >> 1;
	build(lson);
	build(rson);	
}

void pushup(int o)
{
	maxv[o] = max(maxv[ls], maxv[rs]);
	minv[o] = min(minv[ls], minv[rs]);
}

void pushdown(int o)
{
	if(!mark[o]) return;
	swap(maxv[ls], minv[ls]);
	maxv[ls] = -maxv[ls];
	minv[ls] = -minv[ls];
	swap(maxv[rs], minv[rs]);
	maxv[rs] = -maxv[rs];
	minv[rs] = -minv[rs];
	mark[ls] ^= 1;
	mark[rs] ^= 1;
	mark[o] = 0;
}

void updata1(int o, int L, int R, int q, int v)
{
	if(L == R) {
		maxv[o] = minv[o] = v;
		return;
	}
	pushdown(o);
	int mid = (L + R) >> 1;
	if(q <= mid) updata1(lson, q, v);
	else updata1(rson, q, v);
	pushup(o);
}

void updata2(int o, int L, int R, int ql, int qr)
{
	if(ql <= L && qr >= R) {
		mark[o] ^= 1;
		swap(maxv[o], minv[o]);
		maxv[o] = -maxv[o];
		minv[o] = -minv[o];
		return;
	}
	pushdown(o);
	int mid = (L + R) >> 1;
	if(ql <= mid) updata2(lson, ql, qr);
	if(qr > mid) updata2(rson, ql, qr);
	pushup(o);
}

int query(int o, int L, int R, int ql, int qr)
{
	if(ql <= L && qr >= R) return maxv[o];
	int mid = (L + R) >> 1, ans = -INF;
	pushdown(o);
	if(ql <= mid) ans = max(ans, query(lson, ql, qr));
	if(qr > mid) ans = max(ans, query(rson, ql, qr));
	pushup(o);
	return ans;
}

void solve(int a, int b, int ok)
{
	int f1 = top[a], f2 = top[b], ans = -INF;
	while(f1 != f2) {
		if(dep[f1] < dep[f2]) {
			swap(a, b);
			swap(f1, f2);
		}
		if(ok) updata2(1, 1, z, w[f1], w[a]);
		else ans = max(ans, query(1, 1, z, w[f1], w[a]));
		a = fa[f1], f1 = top[a];
	}

	if(a == b) {
		if(!ok) printf("%d\n", ans);
		return;
	}
	if(dep[a] > dep[b]) swap(a, b);
	if(ok) updata2(1, 1, z, w[son[a]], w[b]);
	else ans = max(ans, query(1, 1, z, w[son[a]], w[b]));
	if(!ok) printf("%d\n", ans);
}

void work(void)
{
	dfs1(1);
	dfs2(1, 1);
	
	build(1, 1, z);
	for(int i = 1; i < n; i++) if(dep[edge[i].v] < dep[edge[i].u]) swap(edge[i].u, edge[i].v);
	for(int i = 1; i < n; i++) updata1(1, 1, z, w[edge[i].v], edge[i].c);
	int a, b;
	while(scanf("%s", ss) == 1) {
		if(ss[0] == 'D') break;
		scanf("%d%d", &a, &b);
		if(ss[0] == 'C') updata1(1, 1, z, w[edge[a].v], b);
		if(ss[0] == 'Q') solve(a, b, 0);
		if(ss[0] == 'N') solve(a, b, 1);
	}
}

int main(void)
{
	int _;
	while(scanf("%d", &_)!=EOF) {
		while(_--) {
			init();
			read();
			work();
		}
	}

	return 0;
}