Hysbz 2243 staining (tree chain splitting)

Hello everyone , I meet you again , I'm the king of the whole stack

The mood of doing the topic ： This question is very thoughtful . Debugging code debugging for a long time . Write segment tree interval merging for the first time .

Their thinking ：

The tree chain splits + Segment tree interval merging

The endpoint of the line segment tree records the color of the left and right intervals . Number of colors . When merging, use the idea of interval merging .

One more thing to note . When changing from one chain to another, it is necessary to infer whether the current node is the same color as the parent node .

Code ：

#include<iostream>
#include<sstream>
#include<map>
#include<cmath>
#include<fstream>
#include<queue>
#include<vector>
#include<sstream>
#include<cstring>
#include<cstdio>
#include<stack>
#include<bitset>
#include<ctime>
#include<string>
#include<cctype>
#include<iomanip>
#include<algorithm>
using namespace std  ;
#define INT __int64
#define L(x)  (x * 2)
#define R(x)  (x * 2 + 1)
const int INF = 0x3f3f3f3f ;
const double esp = 0.0000000001 ;
const double PI = acos(-1.0) ;
const int mod = 1e9 + 7 ;
const int MY = 1400 + 5 ;
const int MX = 100000 + 5 ;
int n ,m ,idx ,num ;
int head[MX] ,ti[MX] ,top[MX] ,dep[MX] ,siz[MX] ,son[MX] ,father[MX] ,g[MX] ;
struct Edge
{
    int v ,next ;
}E[MX*2] ;
void addedge(int u ,int v)
{
    E[num].v = v ; E[num].next = head[u] ; head[u] = num++ ;
    E[num].v = u ; E[num].next = head[v] ; head[v] = num++ ;
}
void dfs_find(int u ,int fa)
{
    dep[u] = dep[fa] + 1 ;
    siz[u] = 1 ;
    son[u] = 0 ;
    father[u] = fa ;
    for(int i = head[u] ;i != -1 ;i = E[i].next)
    {
        int v = E[i].v ;
        if(v == fa)  continue ;
        dfs_find(v ,u) ;
        siz[u] += siz[v] ;
        if(siz[son[u]] < siz[v])  son[u] = v ;
    }
}
void dfs_time(int u ,int fa)
{
    ti[u] = idx++ ;
    top[u] = fa ;
    if(son[u])  dfs_time(son[u] ,top[u]) ;
    for(int i = head[u] ;i != -1 ;i = E[i].next)
    {
        int v = E[i].v ;
        if(v == father[u] || v == son[u])   continue ;
        dfs_time(v ,v) ;
    }
}
struct node
{
    int le ,rt ,lc ,rc ,num ,add ;
}T[MX*4] ;
void build(int x ,int le ,int rt)
{
    T[x].le = le ; T[x].rt = rt ;
    T[x].lc = T[x].rc = T[x].add = -1 ;
    T[x].num = 0 ;
    if(le == rt)  return ;
    int Mid = (le + rt)>>1 ;
    build(L(x) ,le ,Mid) ;
    build(R(x) ,Mid + 1 ,rt) ;
}
void push_down(int x)
{
    if(T[x].add != -1)
    {
        //  Left 
        T[L(x)].lc = T[L(x)].rc = T[L(x)].add = T[x].add ; T[L(x)].num = 1 ;
        //  Right 
        T[R(x)].lc = T[R(x)].rc = T[R(x)].add = T[x].add ; T[R(x)].num = 1 ;
        T[x].add = -1 ;
    }
}
void push_up(int x)
{
    T[x].num = T[L(x)].num + T[R(x)].num ;
    if(T[L(x)].rc == T[R(x)].lc)
            T[x].num -- ;
    T[x].lc = T[L(x)].lc ; T[x].rc = T[R(x)].rc ;
}
void update(int x ,int le ,int rt ,int w)  //  Update an interval 
{
    if(T[x].le == le && T[x].rt == rt)
    {
        T[x].add = w ;
        T[x].lc = w ; T[x].rc = w ; T[x].num = 1 ;
        return ;
    }
    push_down(x) ;
    int Mid = (T[x].le + T[x].rt)>>1 ;
    if(le > Mid)    update(R(x) ,le ,rt ,w) ;
    else if(rt <= Mid)   update(L(x) ,le ,rt ,w) ;
    else
    {
        update(L(x) ,le ,Mid ,w) ;
        update(R(x) ,Mid+1 ,rt ,w) ;
    }
    push_up(x) ;
}
int Query(int x ,int le ,int rt)
{
    if(T[x].le == le && T[x].rt == rt)
        return T[x].num ;
    int Mid = (T[x].le + T[x].rt)>>1 ;
    push_down(x) ;
    if(le > Mid)   return   Query(R(x) ,le ,rt) ;
    else if(rt <= Mid) return   Query(L(x) ,le ,rt) ;
    else
    {
        int mx = 0 ;
        if(T[L(x)].rc == T[R(x)].lc)
             mx = -1 ;
        return  Query(L(x) ,le ,Mid) + Query(R(x) ,Mid+1 ,rt) + mx ;
    }
    push_up(x) ;
}
int Querynode(int x ,int pos)
{
    if(T[x].le == T[x].rt)
        return T[x].lc ;
    int Mid = (T[x].le + T[x].rt)>>1 ;
    push_down(x) ;
    if(pos <= Mid)
           return   Querynode(L(x) ,pos) ;
    else   return   Querynode(R(x) ,pos) ;
    push_up(x) ;
}
void LCAC(int u ,int v ,int w)
{
    while(top[u] != top[v])
    {
        if(dep[top[u]] < dep[top[v]])
             swap(u ,v) ;
        update(1 ,ti[top[u]] ,ti[u] ,w) ;
        u = father[top[u]] ;
    }
    if(dep[u] > dep[v])
         swap(u ,v) ;
    update(1 ,ti[u] ,ti[v] ,w) ;
}
int LCAQ(int u ,int v)
{
    int ans = 0 ;
    while(top[u] != top[v])
    {
        if(dep[top[u]] < dep[top[v]])
             swap(u ,v) ;
        ans += Query(1 ,ti[top[u]] ,ti[u]) ;
        if(Querynode(1 ,ti[top[u]]) == Querynode(1 ,ti[father[top[u]]]))
                      ans-- ;
        u = father[top[u]] ;
    }
    if(dep[u] > dep[v])
        swap(u ,v) ;
    ans += Query(1 ,ti[u] ,ti[v]) ;
    return  ans ;
}
int main()
{
    while(~scanf("%d%d" ,&n ,&m))
    {
        int u ,v ,w ;
        num = 0 ;
        memset(head ,-1 ,sizeof(head)) ;
        for(int i = 1 ;i <= n ; ++i)
            scanf("%d" ,&g[i]) ;
        for(int i = 1 ;i < n ; ++i)
        {
            scanf("%d%d" ,&u ,&v) ;
            addedge(u ,v) ;
        }
        dep[1] = siz[0] = 0 ;
        dfs_find(1 ,1) ;
        idx = 1 ;
        dfs_time(1 ,1) ;
        build(1 ,1 ,n) ;
        for(int i = 1 ;i <= n ; ++i)
            update(1 ,ti[i] ,ti[i] ,g[i]) ;
        char s[5] ;
        for(int i = 0 ;i < m ; ++i)
        {
            scanf("%s" ,s) ;
            scanf("%d%d" ,&u ,&v) ;
            if(s[0] == 'C')
            {
                scanf("%d" ,&w) ;
                LCAC(u ,v ,w) ;
            }
            else if(s[0] == 'Q')
                  printf("%d\n" ,LCAQ(u ,v)) ;
        }
    }
    return 0 ;
}

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