POJ-2528 Mayor's posters （线段树区间更新+离散化）

题目分析：线段树区间更新+离散化

代码如下：

# include<iostream>
# include<cstdio>
# include<queue>
# include<vector>
# include<list>
# include<map>
# include<set>
# include<cstdlib>
# include<string>
# include<cstring>
# include<algorithm>
using namespace std;
# define LL long long

const int N=10000;
const int INF=1<<30;
const double oo=1e20;
const double eps=1e-20;

int x[N+5],y[N+5];
vector<int>v;
map<int,int>mp;
int lazy[N*8+5];
int tr[N*8+5];
set<int>s;

void pushDown(int o,int l,int r)
{
	if(lazy[o]!=-1){
		lazy[o<<1]=lazy[o<<1|1]=lazy[o];
		tr[o<<1]=tr[o<<1|1]=lazy[o];
		lazy[o]=-1;
	}
}

void build(int o,int l,int r)
{
	tr[o]=-1;
	lazy[o]=-1;
	if(l==r) return ;
	int mid=l+(r-l)/2;
	build(o<<1,l,mid);
	build(o<<1|1,mid+1,r);
}

void update(int o,int l,int r,int L,int R,int val)
{
	if(L<=l&&r<=R){
		tr[o]=lazy[o]=val;
	}else{
		pushDown(o,l,r);
		int mid=l+(r-l)/2;
		if(L<=mid) update(o<<1,l,mid,L,R,val);
		if(R>mid) update(o<<1|1,mid+1,r,L,R,val);
	}
}

void query(int o,int l,int r)
{
	if(l==r){
		if(tr[o]!=-1) s.insert(tr[o]);
	}else{
		pushDown(o,l,r);
		int mid=l+(r-l)/2;
		query(o<<1,l,mid);
		query(o<<1|1,mid+1,r);
	}
}

int solve(int m,int n)
{
	build(1,1,m);
	for(int i=0;i<n;++i){
		update(1,1,m,mp[x[i]],mp[y[i]],i);
	}
	s.clear();
	query(1,1,m);
	return s.size();
}

int main()
{
	int T,n;
	scanf("%d",&T);
	while(T--)
	{
		mp.clear();
		v.clear();
		scanf("%d",&n);
		for(int i=0;i<n;++i){
			scanf("%d%d",x+i,y+i);
			v.push_back(x[i]);
			v.push_back(y[i]);
		}
		sort(v.begin(),v.end());
		int len=unique(v.begin(),v.end())-v.begin();
		for(int i=0;i<len;++i)
			mp[v[i]]=i+1;
		printf("%d\n",solve(len,n));
	}
	return 0;
}