[线段树] bzoj5029: 贴小广告

bzoj5029: 贴小广告：http://www.lydsy.com/JudgeOnline/problem.php?id=5029

离散化之后用线段树维护
太久没写线段树离散化都不会打了

#include 
#include 
#include 
using namespace std;
struct node1
{
    int l,r,c,lc,rc;
    int lazy;
}tr[210000]; int len=0;
struct node2
{
    int l,r,p;
}a[110000]; 
struct node3
{
    int p,x;
}b[210000];
int ans=0;
bool v[110000];
bool cmp(node3 x,node3 y)//sort 0交换1不交换 
{
    return x.x<y.x;
}
int buildtr(int l,int r)
{
    int mid=(l+r)/2;
    tr[++len].l=l;tr[len].r=r;tr[len].c=0;
    tr[len].lc=tr[len].rc=-1;tr[len].lazy=0;
    int x=len;
    if (l!=r) 
    {
        tr[x].lc=buildtr(l,mid);
        tr[x].rc=buildtr(mid+1,r);
    } 
    return x;
}
void update(int x)
{
    int lc=tr[x].lc,rc=tr[x].rc,k=tr[x].lazy;
    tr[lc].c=tr[lc].lazy=tr[rc].lazy=tr[rc].c=k;
    tr[x].lazy=0;
}
void change(int x,int l,int r,int c)
{
    if (tr[x].l==l&&tr[x].r==r) {tr[x].c=c;tr[x].lazy=c;return ;}
    int mid=(tr[x].l+tr[x].r)/2;
    int lc=tr[x].lc,rc=tr[x].rc;
    if (tr[x].lazy) update(x);
    if (r<=mid) change(lc,l,r,c);
    else if (l>mid) change(rc,l,r,c);
    else {change(lc,l,mid,c);change(rc,mid+1,r,c);}
    if (tr[lc].c==tr[rc].c) tr[x].c=tr[lc].c; else tr[x].c=-1;
}
void solve(int x)
{
    int c=tr[x].c;
    if (c>0)
    {
        if (v[c]) {v[c]=false;ans++;}
    }
    else 
    {
        solve(tr[x].lc);solve(tr[x].rc);
    }
}
int main()
{
    int n;
    scanf("%d",&n);
    for (int i=1;i<=n;i++) 
    {
        scanf("%d%d",&a[i].l,&a[i].r);
        a[i].p=i;
        b[2*i-1].x=a[i].l;
        b[2*i-1].p=i;
        b[2*i].x=a[i].r;
        b[2*i].p=-i;
    }
    sort(b+1,b+1+2*n,cmp);
    b[1].x=1;
    int num=0;
    for (int i=1;i<=2*n;i++)
    {
        if (i==1||b[i].x!=b[i-1].x) num++;
        if (b[i].p<0) a[-b[i].p].r=num;
        else a[b[i].p].l=num;
    }
    buildtr(1,num);
    for (int i=1;i<=n;i++)
    {
        change(1,a[i].l,a[i].r,i);
    }
    memset(v,1,sizeof(v));
    solve(1);
    printf("%d\n",ans);
    return 0;
}