LUOGU P4560 [IOI2014]Wall 砖墙 (线段树)

传送门

解题思路

　　线段树打标记，刚开始想复杂了，维护了四个标记。后来才知道只需要维护一个最大值最小值即可，然后更新的时候分类讨论一下。

代码

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>

using namespace std;
const int MAXN = 2000005;

inline int rd(){
	int x=0,f=1;char ch=getchar();
	while(!isdigit(ch)) {f=ch=='-'?0:1;ch=getchar();}
	while(isdigit(ch))  {x=(x<<1)+(x<<3)+ch-'0';ch=getchar();}
	return f?x:-x;
}

int n,a[MAXN],high[MAXN<<2],low[MAXN<<2],m;

inline int min(int x,int y){
	return x<y?x:y;
}

inline int max(int x,int y){
	return x>y?x:y;
}

inline void pushdown(int x,int l,int r){
	int mid=(l+r)>>1;
	if(l==r) {
		if(low[x]!=-1) a[l]=min(a[l],low[x]);
		if(high[x]!=-1) a[l]=max(a[l],high[x]);
		return ;
	}
	if(low[x]!=-1) {
		if(low[x<<1]!=-1) low[x<<1]=min(low[x<<1],low[x]);
		else low[x<<1]=low[x];
		if(high[x<<1]>low[x]) high[x<<1]=low[x];
		if(low[x<<1|1]!=-1) low[x<<1|1]=min(low[x<<1|1],low[x]);
		else low[x<<1|1]=low[x];
		if(high[x<<1|1]>low[x]) high[x<<1|1]=low[x];
		low[x]=-1;
	}
	if(high[x]!=-1){
		high[x<<1]=max(high[x<<1],high[x]);
		if(high[x]>low[x<<1] && low[x<<1]!=-1) low[x<<1]=high[x];
		high[x<<1|1]=max(high[x<<1|1],high[x]);
		if(high[x]>low[x<<1|1] && low[x<<1|1]!=-1) low[x<<1|1]=high[x];
		high[x]=-1;
	}
}

void update_h(int x,int l,int r,int L,int R,int k){
	if(L<=l && r<=R) {
		high[x]=max(high[x],k);
		if(low[x]!=-1 && low[x]<k) low[x]=k;
		if(l==r) {
			if(low[x]!=-1) a[l]=min(a[l],low[x]);
			if(high[x]!=-1) a[l]=max(a[l],high[x]);
		}
		return ;
	}
	int mid=(l+r)>>1;pushdown(x,l,r);
	if(L<=mid) update_h(x<<1,l,mid,L,R,k);
	if(mid<R)  update_h(x<<1|1,mid+1,r,L,R,k);
}

void update_l(int x,int l,int r,int L,int R,int k){
	if(L<=l && r<=R) {
		if(low[x]==-1) low[x]=k;
		else low[x]=min(low[x],k);
		if(high[x]!=-1 && high[x]>k) high[x]=k;
		if(l==r){
			if(low[x]!=-1) a[l]=min(a[l],low[x]);
			if(high[x]!=-1) a[l]=max(a[l],high[x]);
		}
		return ;
	}
	int mid=(l+r)>>1;pushdown(x,l,r);
	if(L<=mid) update_l(x<<1,l,mid,L,R,k);
	if(mid<R) update_l(x<<1|1,mid+1,r,L,R,k);
}

void query(int x,int l,int r){
	if(l==r) {pushdown(x,l,r);printf("%d\n",a[l]);return ;}
	int mid=(l+r)>>1;pushdown(x,l,r);
	query(x<<1,l,mid);query(x<<1|1,mid+1,r);
}

int main(){
	memset(low,-1,sizeof(low));
	memset(high,-1,sizeof(high));
	n=rd(),m=rd();int op,l,r,k;
	while(m--){
		op=rd(),l=rd(),r=rd(),k=rd();l++;r++;
		if(op==1) update_h(1,1,n,l,r,k);
		else update_l(1,1,n,l,r,k);
	}
	query(1,1,n);
	return 0;
}