poj3614 二分图最大匹配 or 贪心

Sunscreen

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 5926		Accepted: 2072

Description

To avoid unsightly burns while tanning, each of the C (1 ≤ C ≤ 2500) cows must cover her hide with sunscreen when they're at the beach. Cow i has a minimum and maximum SPF rating (1 ≤ minSPF_i ≤ 1,000; minSPF_i ≤ maxSPF_i ≤ 1,000) that will work. If the SPF rating is too low, the cow suffers sunburn; if the SPF rating is too high, the cow doesn't tan at all........

The cows have a picnic basket with L (1 ≤ L ≤ 2500) bottles of sunscreen lotion, each bottle i with an SPF rating SPF_i (1 ≤ SPF_i ≤ 1,000). Lotion bottle i can cover cover_i cows with lotion. A cow may lotion from only one bottle.

What is the maximum number of cows that can protect themselves while tanning given the available lotions?

Input

* Line 1: Two space-separated integers: C and L
* Lines 2..C+1: Line i describes cow i's lotion requires with two integers: minSPF_i and maxSPF_i
* Lines C+2..C+L+1: Line i+C+1 describes a sunscreen lotion bottle i with space-separated integers: SPF_i and cover_i

Output

A single line with an integer that is the maximum number of cows that can be protected while tanning

Sample Input

3 2
3 10
2 5
1 5
6 2
4 1

Sample Output

2

题意: 给定n个区间, m个值以及这个值对应的数目, 求区间与值的最大匹配;

分析:开始看到n不是太大, 果断想到了用二分图的最大匹配, 只是这个匹配是有数目要求的,

但是变化一下就行了.

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贪心策略: 把区间按照左边界排序, 把值按照大小排序, 然后遍历每个值, 把左边界小于当前值的区间全部扔到multiset中, 每次取右边界距离当前的值最近的区间进行贪心,

因为值是逐渐增大的, 右边界越大的区间, 选择也就越大.

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