bzoj1828: [Usaco2010 Mar]balloc 农场分配 线段树+贪心

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<iostream>
#define fo(i,a,b) for(int i=a;i<=b;i++)
#define fd(i,a,b) for(int i=a;i>=b;i--)
using namespace std;
const int N=1e5+5;
const int inf=1e9+5;
struct data
{
int l,r;
int mn,lazy;
}t[N*10];
struct node
{
int l,r,id;
}q
;
int a
,ans;
int n,m;
bool cmp(node a,node b)
{
return (a.r<b.r);
}
inline void build(int x,int l,int r)
{
t[x].l=l;
t[x].r=r;
if (l==r)
{
t[x].mn=a[l];
return ;
}
int mid=(l+r)>>1;
build(x<<1,l,mid);
build(x<<1|1,mid+1,r);
t[x].mn=min(t[x<<1].mn,t[x<<1|1].mn);
}
inline void pushdown(int x)
{
int ls=x<<1,rs=x<<1|1;
t[ls].mn+=t[x].lazy;
t[rs].mn+=t[x].lazy;
t[ls].lazy+=t[x].lazy;
t[rs].lazy+=t[x].lazy;
t[x].lazy=0;
}
inline void change(int x,int l,int r)
{
if (t[x].l==l&&t[x].r==r)
{
t[x].mn--;
t[x].lazy--;
return ;
}
if (t[x].lazy)pushdown(x);
int mid=(t[x].l+t[x].r)>>1;
if (r<=mid)change(x<<1,l,r);
else if (l>mid)change(x<<1|1,l,r);
else change(x<<1,l,mid),change(x<<1|1,mid+1,r);
t[x].mn=min(t[x<<1].mn,t[x<<1|1].mn);
}
inline int query(int x,int l,int r)
{
if (t[x].l==l&&t[x].r==r)
{
return t[x].mn;
}
if (t[x].lazy)pushdown(x);
int mid=(t[x].l+t[x].r)>>1;
if (r<=mid)return query(x<<1,l,r);
else if (l>mid)return query(x<<1|1,l,r);
else return min(query(x<<1,l,mid),query(x<<1|1,mid+1,r));
}
int main()
{
scanf("%d%d",&n,&m);
fo(i,1,n)scanf("%d",&a[i]);
build(1,1,n);
fo(i,1,m)
{
scanf("%d%d",&q[i].l,&q[i].r);
q[i].id=i;
}
sort(q+1,q+1+m,cmp);
fo(i,1,m)
{
if (query(1,q[i].l,q[i].r))
change(1,q[i].l,q[i].r),++ans;
}
printf("%d\n",ans);
return 0;
}