BZOJ 1828: [Usaco2010 Mar]balloc 农场分配

#include<cstdio>
#include<cstring>
#include<algorithm>
//by zrt
//problem:
using namespace std;
int minn[100005*4];
int mark[100005*4];
int c[100005];
void pd(int o){
    if(mark[o]){
        minn[o<<1]-=mark[o];
        minn[o<<1|1]-=mark[o];
        mark[o<<1]+=mark[o];
        mark[o<<1|1]+=mark[o];
        mark[o]=0;
    }
}
void insert(int o,int l,int r,int L,int R){
    if(l==L&&r==R){
        mark[o]+=1;
        minn[o]-=1;
        return;
    }else{
        pd(o);
        int m=(L+R)>>1;
        if(r<=m) insert(o<<1,l,r,L,m);
        else if(l>m) insert(o<<1|1,l,r,m+1,R);
        else insert(o<<1,l,m,L,m),insert(o<<1|1,m+1,r,m+1,R);
        minn[o]=min(minn[o<<1],minn[o<<1|1]);
    }
}
void build(int o,int l,int r){
    if(l==r){
        minn[o]=c[l];
    }else{
        int m=(l+r)>>1;
        build(o<<1,l,m);
        build(o<<1|1,m+1,r);
        minn[o]=min(minn[o<<1],minn[o<<1|1]);
    }
}
bool ok;
void ask(int o,int l,int r,int L,int R){
    if(l==L&&r==R)  ok&=(minn[o]>0);
    else{
        pd(o);
        int m=(L+R)>>1;
        if(r<=m) ask(o<<1,l,r,L,m);
        else if(l>m) ask(o<<1|1,l,r,m+1,R);
        else ask(o<<1,l,m,L,m),ask(o<<1|1,m+1,r,m+1,R);
    }
}
struct node{
    int a,b;
}q[100005];
bool cmp(node a,node b){
    return a.b<b.b;
}
int main(){
    #ifdef LOCAL
    freopen("in.txt","r",stdin);
    freopen("out.txt","w",stdout);
    #endif
    int n,m;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++){
        scanf("%d",&c[i]);
    }
    for(int i=0;i<m;i++){
        scanf("%d%d",&q[i].a,&q[i].b);
    }
    sort(q,q+m,cmp);
    int ans=0;
    build(1,1,n);
    for(int i=0;i<m;i++){
        ok=1;ask(1,q[i].a,q[i].b,1,n);
        if(ok){
            ans++;
            insert(1,q[i].a,q[i].b,1,n);
        }
    }
    printf("%d\n",ans);
    return 0;
}