POJ 2528 Mayor's posters(线段树，区间覆盖，单点查询)

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <cmath>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <stack>
#include <algorithm>
using namespace std;
#define root 1,n,1
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define lr rt<<1
#define rr rt<<1|1
typedef long long LL;
const int oo = 1e9+7;
const double PI = acos(-1.0);
const double eps = 1e-6 ;
const int N =  20010;
const int mod = 2333333;
int n , m ;
LL col[N<<2] , tot ;
bool tag[N<<2] ;

void Down( int l , int r , int rt ) {
    if( col[rt] != -1 ) col[lr] = col[rr] = col[rt] ;
}
void Up( int rt ){
    if( col[lr] == col[rr] && col[lr] != -1 ) col[rt] = col[lr];
    else col[rt] = -1 ;
}
void build( int l , int r , int rt ){
    col[rt] = -1 ;
    if( l == r ) return ;
    int mid = (l+r)>>1;
    build(lson),build(rson);
}
void update( int l , int r , int rt , int L , int R , int c ) {
//    cout << L <<‘ ‘ << R << ‘ ‘ << l << ‘ ‘ << r << endl ;
    if( L == l && r == R ) {
        col[rt] = c ; return ;
    }
    if( col[rt] == c ) return ;
    else Down( l,r,rt ) , col[rt] = -1 ;
    int mid = (l+r)>>1;
    if( R <= mid ) update(lson,L,R,c);
    else if( L > mid ) update(rson,L,R,c);
    else update(lson,L,mid,c) , update(rson,mid+1,R,c);
    Up(rt);
}
LL query( int l , int r , int rt , int x ) {
    if( col[rt] != -1 ) return col[rt];
    Down(l,r,rt);
    int mid = (l+r)>>1;
    if( x <= mid ) return query(lson,x);
    else return query(rson,x);
}
struct node {
    int num , new_num , id ;
}e[N];
bool cmp1( const node &a , const node &b ) { return a.num < b.num ; }
bool cmp2( const node &a , const node &b ) { return a.id < b.id ; }

int main()
{
    #ifdef LOCAL
        freopen("in.txt","r",stdin);
//        freopen("out.txt","w",stdout);
    #endif // LOCAL
    int _ ; scanf("%d",&_);
    while( _-- ) {
        memset( tag , false , sizeof tag );
        tot = 0 ; scanf("%d",&n);
        for( int i = 0 ; i < n ; ++i ) {
            scanf("%d",&e[tot].num); e[tot].id = tot ; tot++;
            scanf("%d",&e[tot].num); e[tot].id = tot ; tot++;
        }
        sort( e , e + tot , cmp1 );
        e[0].new_num = 1 ;
        for( int i = 1 ; i < tot ; ++i )
            e[i].new_num = (e[i].num == e[i-1].num?e[i-1].new_num:e[i-1].new_num+1);
        sort( e , e + tot , cmp2 );
        n = tot+10;
        build(root);
        for( int i = 0 ; i < tot ; i+=2 ){
//            cout << e[i].new_num << ‘ ‘ << e[i+1].new_num << endl ;
            update(root,e[i].new_num,e[i+1].new_num,i+1);
        }
//        cout << "ok" << endl ;
        for( int i = 1 ; i <= n ; ++i ) {
//            cout <<  query(root,i) << endl ;
            int color = query(root,i) ;
            if( color == -1 ) continue ;
            tag[color] = true ;
        }
        int ans = 0 ;
        for( int i = 1 ; i <= n ; ++i ) if(tag[i]) ans++;
        printf("%d\n",ans);
    }
}