CF1132C Painting the Fence

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  • 题目来源 CodeForces 1132C
  • 评测方式 RemoteJudge
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  • 难度 提高+/省选-
  • 时空限制 2000ms / 256MB

题解

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    题意翻译

    题意描述

    墙长为n,q个工人,每个工人固定粉刷一个区间,区间可能重叠,现在要去掉两个工人,求剩下q-2个工人最多粉刷多少墙。(3≤n,q≤5000 ) (1 ≤ l i ≤ r i ≤n)

    题目描述

    You have a long fence which consists of $ n $ sections. Unfortunately, it is not painted, so you decided to hire $ q $ painters to paint it. $ i $ -th painter will paint all sections $ x $ such that $ l_i \le x \le r_i $ .

    Unfortunately, you are on a tight budget, so you may hire only $ q - 2 $ painters. Obviously, only painters you hire will do their work.

    You want to maximize the number of painted sections if you choose $ q - 2 $ painters optimally. A section is considered painted if at least one painter paints it.

    输入输出格式

    输入格式:

    The first line contains two integers $ n $ and $ q $ ( $ 3 \le n, q \le 5000 $ ) — the number of sections and the number of painters availible for hire, respectively.

    Then $ q $ lines follow, each describing one of the painters: $ i $ -th line contains two integers $ l_i $ and $ r_i $ ( $ 1 \le l_i \le r_i \le n $ ).

    输出格式:

    Print one integer — maximum number of painted sections if you hire $ q - 2 $ painters.

    输入输出样例

    输入样例#1: 复制
    7 5
    1 4
    4 5
    5 6
    6 7
    3 5
    
    输出样例#1: 复制
    7
    
    输入样例#2: 复制
    4 3
    1 1
    2 2
    3 4
    
    输出样例#2: 复制
    2
    
    输入样例#3: 复制
    4 4
    1 1
    2 2
    2 3
    3 4
    
    输出样例#3: 复制
    3
    
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