[bzoj1029][JSOI2007]建筑抢修【贪心】【堆】

/* --------------
user Vanisher
problem bzoj-1029
----------------*/
# include <bits/stdc++.h>
# define    ll      long long
# define    N       200010
using namespace std;
int read(){
int tmp=0, fh=1; char ch=getchar();
while (ch<'0'||ch>'9'){if (ch=='-') fh=-1; ch=getchar();}
while (ch>='0'&&ch<='9'){tmp=tmp*10+ch-'0'; ch=getchar();}
return tmp*fh;
}
struct node{
int a,b;
}t
;
bool cmp(node a, node b){
return a.b<b.b;
}
priority_queue <int> hp;
int n,now,num;
int main(){
n=read();
for (int i=1; i<=n; i++)
t[i].a=read(), t[i].b=read();
sort(t+1,t+n+1,cmp);
now=0; num=0;
for (int i=1; i<=n; i++){
now=now+t[i].b-t[i-1].b;
if (now>=t[i].a){
hp.push(t[i].a);
now-=t[i].a;
num++;
}
else {
if (t[i].a<hp.top()){
now=now+hp.top()-t[i].a;
hp.pop(); hp.push(t[i].a);
}
}
}
printf("%d\n",num);
return 0;
}