【POJ】3237 Tree 树链剖分

传送门：【POJ】3237 Tree

题目分析：树链剖分水题。线段树每个区间两个变量，minv表示区间最小值，maxv表示区间最大值，区间取反的时候swap( minv , maxv )，然后minv = -minv，maxv = -maxv即可，因为最小值变成了最大值，最大值变成了最小值。

代码如下：

#include <cmath>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std ;

typedef long long LL ;

#define travel( e , H , u ) for ( Edge* e = H[u] ; e ; e = e -> next )
#define rep( i , a , b ) for ( int i = ( a ) ; i <  ( b ) ; ++ i )
#define rev( i , a , b ) for ( int i = ( a ) ; i >= ( b ) ; -- i )
#define FOR( i , a , b ) for ( int i = ( a ) ; i <= ( b ) ; ++ i )
#define clr( a , x ) memset ( a , x , sizeof a )
#define cpy( a , x ) memcpy ( a , x , sizeof a )
#define ls ( o << 1 )
#define rs ( o << 1 | 1 )
#define lson ls , l , m
#define rson rs , m + 1 , r
#define root 1 , 2 , n
#define mid ( ( l + r ) >> 1 )

const int MAXN = 10005 ;
const int MAXE = 20005 ;
const int INF = 0x3f3f3f3f ;

struct Edge {
	int v ;
	Edge* next ;
} E[MAXE] , *H[MAXN] , *edge ;

struct Line {
	int x , y , w ;
	Line () {}
	Line ( int x , int y , int w ) : x ( x ) , y ( y ) , w ( w ) {}
} L[MAXN] ;

int maxv[MAXN << 2] ;
int minv[MAXN << 2] ;
bool set[MAXN << 2] ;
int siz[MAXN] ;
int pos[MAXN] ;
int pre[MAXN] ;
int top[MAXN] ;
int dep[MAXN] ;
int son[MAXN] ;
int val[MAXN] ;
int tree_idx ;
int n ;

void clear () {
	edge = E ;
	tree_idx = 0 ;
	clr ( H , 0 ) ;
	clr ( set , 0 ) ;
	pre[1] = 0 ;
	siz[0] = 0 ;
	dep[0] = 0 ;
}

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

void dfs ( int u ) {
	siz[u] = 1 ;
	son[u] = 0 ;
	travel ( e , H , u ) {
		int v = e -> v ;
		if ( v != pre[u] ) {
			pre[v] = u ;
			dep[v] = dep[u] + 1 ;
			dfs ( v ) ;
			siz[u] += siz[v] ;
			if ( siz[v] > siz[son[u]] ) son[u] = v ;
		}
	}
}

void rewrite ( int u , int top_element ) {
	top[u] = top_element ;
	pos[u] = ++ tree_idx ;
	if ( son[u] ) rewrite ( son[u] , top_element ) ;
	travel ( e , H , u ) {
		int v = e -> v ;
		if ( v != son[u] && v != pre[u] ) rewrite ( v , v ) ;
	}
}

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

inline void fun ( int o ) {
	set[o] ^= 1 ;
	swap ( minv[o] , maxv[o] ) ;
	minv[o] = -minv[o] ;
	maxv[o] = -maxv[o] ;
}

inline void pushdown ( int o ) {
	if ( set[o] ) {
		fun ( ls ) ;
		fun ( rs ) ;
		set[o] = 0 ;
	}
}

void build ( int o , int l , int r ) {
	if ( l == r ) {
		minv[o] = maxv[o] = val[l] ;
		return ;
	}
	int m = mid ;
	build ( lson ) , build ( rson ) ;
	pushup ( o ) ;
}

void sub_update ( int L , int R , int o , int l , int r ) {
	if ( L <= l && r <= R ) {
		fun ( o ) ;
		return ;
	}
	int m = mid ;
	pushdown ( o ) ;
	if ( L <= m ) sub_update ( L , R , lson ) ;
	if ( m <  R ) sub_update ( L , R , rson ) ;
	pushup ( o ) ;
}

void update ( int x , int y ) {
	while ( top[x] != top[y] ) {
		if ( dep[top[x]] < dep[top[y]] ) swap ( x , y ) ;
		sub_update ( pos[top[x]] , pos[x] , root ) ;
		x = pre[top[x]] ;
	}
	if ( x == y ) return ;
	if ( dep[x] > dep[y] ) swap ( x , y ) ;
	sub_update ( pos[x] + 1 , pos[y] , root ) ;
}

void modify ( int pos , int v , int o , int l , int r ) {
	while ( l != r ) {
		int m = mid ;
		pushdown ( o ) ;
		if ( pos <= m ) r = m , o = ls ;
		else l = m + 1 , o = rs ;
	}
	minv[o] = maxv[o] = v ;
	while ( o != 1 ) {
		o >>= 1 ;
		pushup ( o ) ;
	}
}

int sub_query ( int L , int R , int o , int l , int r ) {
	if ( L <= l && r <= R ) return maxv[o] ;
	int m = mid ;
	pushdown ( o ) ;
	if ( R <= m ) return sub_query ( L , R , lson ) ;
	if ( m <  L ) return sub_query ( L , R , rson ) ;
	return max ( sub_query ( L , R , lson ) , sub_query ( L , R , rson ) ) ;
}

int query ( int x , int y , int res = -INF ) {
	while ( top[x] != top[y] ) {
		if ( dep[top[x]] < dep[top[y]] ) swap ( x , y ) ;
		res = max ( res , sub_query ( pos[top[x]] , pos[x] , root ) ) ;
		x = pre[top[x]] ;
	}
	if ( x == y ) return res ;
	if ( dep[x] > dep[y] ) swap ( x , y ) ;
	return max ( res , sub_query ( pos[x] + 1 , pos[y] , root ) ) ;
}

void solve () {
	char buf[10] ;
	int x , y , w ;
	clear () ;
	scanf ( "%d" , &n ) ;
	rep ( i , 1 , n ) {
		scanf ( "%d%d%d" , &x , &y , &w ) ;
		L[i] = Line ( x , y , w ) ;
		addedge ( x , y ) ;
	}
	dfs ( 1 ) ;
	rewrite ( 1 , 1 ) ;
	rep ( i , 1 , n ) {
		if ( dep[L[i].x] < dep[L[i].y] ) swap ( L[i].x , L[i].y ) ;
		val[pos[L[i].x]] = L[i].w ;
	}
	build ( root ) ;
	while ( ~scanf ( "%s" , buf ) && buf[0] != 'D' ) {
		scanf ( "%d%d" , &x , &y ) ;
		if ( buf[0] == 'C' ) modify ( pos[L[x].x] , y , root ) ;
		else if ( buf[0] == 'N' ) update ( x , y ) ;
		else printf ( "%d\n" , query ( x , y ) ) ;
	}
}

int main () {
	int T ;
	scanf ( "%d" , &T ) ;
	while ( T -- ) solve () ;
	return 0 ;
}