SPOJ QTREE3 Query on a tree again! (Chain split tree)

Topic link: https: //vjudge.net/contest/314922#problem/B

#include <cmath>
#include <cstdio>
#include <algorithm>
#include <iostream>
#include <cstring>
#include <ctype.h>
#include <map>
#include <vector>
#include <set>
#include <bitset>
#define lson rt << 1, l, mid
#define rson rt << 1 | 1, mid + 1, r
#define lc rt << 1
#define rc rt << 1 | 1
#define INF 0x7fffffff
#define eps 1e-9
#define pi acos(-1.0)
using namespace std;
typedef long long ll;
static const int MAX_N = 1e5 + 5;
static const int Mod = 10007;
struct Edge{
    int to, next;
}edge[MAX_N << 1];
int head[MAX_N];    //链式前向星
int siz[MAX_N], son[MAX_N], top[MAX_N], fa[MAX_N], tid[MAX_N], dep[MAX_N], pos[MAX_N];
int cnt, tot;
void dfs1(int u, int f, int d){     //The first son of a weight dfs 
    SIZ [U] = . 1 ; 
    DEP [U] = D; 
    Son [U] = 0 ; 
    FA [U] = F;
     for ( int I = head [U];! = I - . 1 ; I = Edge [I] .next) {
         int V = Edge [I] .to;
         IF (V == F) Continue ;     // do not take repeated passage 
        DFS1 (V, U, D + . 1 ); 
        SIZ [U ] + = SIZ [V];
         IF (SIZ [V]> SIZ [Son [U]]) Son [U] = V; 
    } 
} 
voidDFS2 ( int U, int T) {      // the son ligation into a heavy chain, light son connected light chain (obtained interval) 
    Top [U] = T; 
    TID [U] = ++ CNT; 
    POS [CNT] = U;
     IF (Son [U]) DFS2 (Son [U], T);   // priority of the heavy chain 
    for ( int I = head [U]; I = -! . 1 ; I = Edge [I] .next) {
         int V = Edge [I] .to;
         IF (!! V Son = [U] && V = FA [U]) DFS2 (V, V); 
    } 
} 
int Tag [MAX_N << 2 ];
 void prework ( ) { 
    Memset ( head, -1, sizeof(head));
    memset(tag, 0, sizeof(tag));
    cnt = 0;
    tot = 0;
}
void addEdge(int u, int v){
    edge[tot].to = v;
    edge[tot].next = head[u];
    head[u] = tot++;
}
void pushUp(int rt){
    tag[rt] = tag[lc] + tag[rc];
}
void update(int rt, int l, int r, int pos){
    if(l == r){
        tag[rt] ^= 1;
        return ;
    }
    int mid = l + r >> 1;
    if(pos <= mid) update(lson, pos);
    else update(rson, pos);
    pushUp(rt);
}
int queryInd(int rt, int l, int r, int ql, int qr){
    if(!tag[rt]) return -1;
    if(l == r) return pos[l];
    int mid = l + r >> 1;
    int ans = -1;
    if(ql <= mid) ans = queryInd(lson, ql, qr);
    if(ans != -1) return ans;
    if(qr > mid) ans = queryInd(rson, ql, qr);
    return ans;
}
int queryPathInd(int u, int v){
    int ans = -1, temp;
    while(top[u] != top[v]){
        if(dep[top[u]] < dep[top[v]]) swap(u, v);
        temp = queryInd(1, 1, cnt, tid[top[u]], tid[u]);
        if(temp != -1) ans = temp;
        u = fa[top[u]];
    }
    if(dep[u] > dep[v]) swap(u, v);
    temp = queryInd(1, 1, cnt, tid[u], tid[v]);  //后面离的越近
    if(temp != -1) ans = temp;
    return ans;
}
void mainwork(){
    int n, q;
    scanf("%d%d", &n, &q);
    for(int i = 1; i < n; ++i){
        int u, v;
        scanf("%d%d", &u, &v);
        addEdge(u, v);
        addEdge(v, u);
    }
    dfs1(1, 0, 1);
    dfs2(1, 1);
    while(q--){
        int opt, x;
        scanf("%d%d", &opt, &x);
        if(opt) printf("%d\n", queryPathInd(1, x));
        else update(1, 1, cnt, tid[x]);
    }
}
int main(){
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
    prework();
    mainwork();
    return 0;
}

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