hdu 4268 Alice and Bob(multiset)

# include<stdio.h>
# include<algorithm>
# include<iostream>
# include<string.h>
# include<map>
# include<set>
# include<vector>
using namespace std;
struct node
{
    int h;
    int w;
};
struct node a[100010],b[100010];
bool cmp(node a1,node a2)
{
    if(a1.h==a2.h)
        return a1.w<a2.w;
    return a1.h<a2.h;
}
int main()
{
    int t,i,n,p;
    multiset<int>num;///可以插入相同元素，set只能插入不同元素
    multiset<int>::iterator it;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d",&n);
        for(i=0; i<n; i++)
            scanf("%d%d",&a[i].h,&a[i].w);
        for(i=0; i<n; i++)
            scanf("%d%d",&b[i].h,&b[i].w);
        sort(a,a+n,cmp);
        sort(b,b+n,cmp);
        int p=0;
        int ans=0;
        num.clear();
        for(i=0; i<n; i++)
        {
            while(p<n&&a[i].h>=b[p].h)
            {
                num.insert(b[p].w);
                p++;
            }
            if(num.empty())
                continue;
            it=num.upper_bound(a[i].w);///返回大于等于a[i].w的第一个元素 //set
            if(it!=num.begin())
            {
                ans++;
                it--;///小于a[i].w
                num.erase(it);///相同的元素都会删除
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}