线段树典型例题--poj3667 hotel

题目很像内存分配。

线段树维护这样几个量：

col：节点的颜色（0--没有覆盖，1--全覆盖，-1--有多种颜色）

dl：从左边开始的最长连续段

dr：从右边开始的最长连续段

dm：节点中的最长连续段

dp：节点中最长连续段的开始位置

具体见代码：

#include <iostream>
#include <cstring>
#include <string>
#include <cstdio>
#include <algorithm>
using namespace std;

const int N=400000;

int dl
,dr
,dm
,dp
,col
,l
,r
;
bool pp
;
int n,m;

void build(int i,int ll,int rr)
{
l[i]=ll;r[i]=rr;
dl[i]=dr[i]=dm[i]=r[i]-l[i]+1;
col[i]=0;
dp[i]=l[i];
pp[i]=false;
if (l[i]==r[i]) return;
int mid=(l[i]+r[i])/2;
build(i*2,l[i],mid);
build(i*2+1,mid+1,r[i]);
}

void down(int i)
{
if (!pp[i]) return;
col[i*2]=col[i*2+1]=col[i];
if (col[i]==0)
{
dl[i*2]=dr[i*2]=dm[i*2]=r[i*2]-l[i*2]+1;
dp[i*2]=l[i*2];
dl[i*2+1]=dr[i*2+1]=dm[i*2+1]=r[i*2+1]-l[i*2+1]+1;
dp[i*2+1]=l[i*2+1];
}
else
{
dl[i*2]=dr[i*2]=dm[i*2]=0;
dl[i*2+1]=dr[i*2+1]=dm[i*2+1]=0;
}
pp[i]=false;
pp[i*2]=true;pp[i*2+1]=true;
}

int find(int i,int k)
{
if (l[i]==r[i])
{
if (dm[i]>=k) return dp[i];
else return 0;
}
if (dm[i]>=k)
{
down(i);
if (dm[i*2]>=k) return find(i*2,k);
else if (dr[i*2]+dl[i*2+1]>=k) return r[i*2]-dr[i*2]+1;
else if (dm[i*2+1]>=k) return find(i*2+1,k);
}
else return 0;
}

void update(int i)
{
if (col[i*2]==0 || col[i*2+1]==0)
{
if (col[i*2+1]==col[i*2]) col[i]=0;
else col[i]=-1;
if (col[i*2]==0) dl[i]=dl[i*2]+dl[i*2+1];
else dl[i]=dl[i*2];
if (col[i*2+1]==0) dr[i]=dr[i*2]+dr[i*2+1];
else dr[i]=dr[i*2+1];
}
else if (col[i*2]==-1 || col[i*2+1]==-1)
{
col[i]=-1;
dl[i]=dl[i*2];
dr[i]=dr[i*2+1];
}
else if (col[i*2]==1 && col[i*2+1]==1)
{
col[i]=1;
dl[i]=dr[i]=0;
}
dm[i]=dm[i*2];dp[i]=dp[i*2];
if (dr[i*2]+dl[i*2+1]>dm[i])
{
dm[i]=dr[i*2]+dl[i*2+1];
dp[i]=r[i*2]-dr[i*2]+1;
}
else if (dr[i*2]+dl[i*2+1]==dm[i] && r[i*2]-dr[i*2]+1<dp[i])
dp[i]=r[i*2]-dr[i*2]+1;
if (dm[i*2+1]>dm[i])
{
dm[i]=dm[i*2+1];
dp[i]=dp[i*2+1];
}
else if (dm[i*2+1]==dm[i] && dp[i*2+1]<dp[i])
dp[i]=dp[i*2+1];
}

void change(int i,int x,int y,int cc)
{
if (x<=l[i] && y>=r[i])
{
col[i]=cc;
if (col[i]==0)
{
dl[i]=dr[i]=dm[i]=r[i]-l[i]+1;
dp[i]=l[i];
}
else dl[i]=dr[i]=dm[i]=0;
pp[i]=true;
return;
}
down(i);
int mid=(l[i]+r[i])/2;
if (x<=mid) change(i*2,x,y,cc);
if (y>mid) change(i*2+1,x,y,cc);
update(i);
}

int main()
{
int i,j,k,d;

freopen("in","r",stdin);
scanf("%d%d",&n,&m);
build(1,1,n);
for (i=1;i<=m;i++)
{
scanf("%d",&j);
if (j==1)
{
scanf("%d",&d);
k=find(1,d);
printf("%d\n",k);
if (k>0) change(1,k,k+d-1,1);
}
else
{
scanf("%d%d",&k,&d);
change(1,k,k+d-1,0);
}
}
}