HDU 4268 Alice and Bob（贪心+STL）

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思路：

分析：对Alice 和Bob的牌都按 h 排序，然后对Alice的每张牌，在Bob的牌中找一个最大能覆盖的。也就是说首先满足Alice的牌 h >= Bob的牌 h，然后找最大 w。在查找最大的w时，可以使用multiset中的lower_bound。multiset动态插入每次只插入满足Alice的牌 h >= Bob的牌 h 的牌。

#include<iostream>#include<algorithm>#include<cstdio>#include<set>#define MAXN 100001using namespace std;multiset<int>ms;struct SS{int w,h;}A[MAXN],B[MAXN];bool cmp(SS p,SS q){    if(p.w<q.w) return true;    return false;}int main(){    int test,n,i,j,ans;    scanf("%d",&test);    while(test--)    {        scanf("%d",&n);        for(i=0;i<n;i++)            scanf("%d%d",&A[i].w,&A[i].h);        for(i=0;i<n;i++)            scanf("%d%d",&B[i].w,&B[i].h);        sort(A,A+n,cmp);        sort(B,B+n,cmp);        ms.clear();        ans=0;        multiset<int>::iterator it;        for(i=0,j=0;i<n;i++)        {            for(;j<n&&A[i].w>=B[j].w;j++)            {                ms.insert(B[j].h);            }            if(ms.empty())continue;            it=ms.lower_bound(A[i].h);            if(it==ms.end()||A[i].h<*it) it--;            if(*it<=A[i].h)            {                ans++;                ms.erase(it);            }        }        printf("%d\n",ans);    }    return 0;}

Description

Alice and Bob's game never ends. Today, they introduce a new game. In this game, both of them have N different rectangular cards respectively. Alice wants to use his cards to cover Bob's. The card A can cover the card B if the height of A is not smaller than B and the width of A is not smaller than B. As the best programmer, you are asked to compute the maximal number of Bob's cards that Alice can cover.
Please pay attention that each card can be used only once and the cards cannot be rotated.

Input

The first line of the input is a number T (T <= 40) which means the number of test cases.
For each case, the first line is a number N which means the number of cards that Alice and Bob have respectively. Each of the following N (N <= 100,000) lines contains two integers h (h <= 1,000,000,000) and w (w <= 1,000,000,000) which means the height and width of Alice's card, then the following N lines means that of Bob's.

Output

For each test case, output an answer using one line which contains just one number.

Sample Input

221 23 42 34 532 35 76 84 12 53 4

Sample Output

0 0