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  • Codeforces Round #241 (Div. 2)->A. Guess a number!

    A. Guess a number!
    time limit per test
    1 second
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    A TV show called "Guess a number!" is gathering popularity. The whole Berland, the old and the young, are watching the show.

    The rules are simple. The host thinks of an integer y and the participants guess it by asking questions to the host. There are four types of acceptable questions:

    • Is it true that y is strictly larger than number x?
    • Is it true that y is strictly smaller than number x?
    • Is it true that y is larger than or equal to number x?
    • Is it true that y is smaller than or equal to number x?

    On each question the host answers truthfully, "yes" or "no".

    Given the sequence of questions and answers, find any integer value of y that meets the criteria of all answers. If there isn't such value, print "Impossible".

    Input

    The first line of the input contains a single integer n (1 ≤ n ≤ 10000) — the number of questions (and answers). Next n lines each contain one question and one answer to it. The format of each line is like that: "sign x answer", where the sign is:

    • ">" (for the first type queries),
    • "<" (for the second type queries),
    • ">=" (for the third type queries),
    • "<=" (for the fourth type queries).

    All values of x are integer and meet the inequation  - 109 ≤ x ≤ 109. The answer is an English letter "Y" (for "yes") or "N" (for "no").

    Consequtive elements in lines are separated by a single space.

    Output

    Print any of such integers y, that the answers to all the queries are correct. The printed number y must meet the inequation - 2·109 ≤ y ≤ 2·109. If there are many answers, print any of them. If such value doesn't exist, print word "Impossible" (without the quotes).

    Examples
    input
    4
    >= 1 Y
    < 3 N
    <= -3 N
    > 55 N
    output
    17
    input
    2
    > 100 Y
    < -100 Y
    output
    Impossible

     题意理解:猜数字,输出猜出的数字中任意一个,如果不符合则输出Impossible”。

     1 #include<bits/stdc++.h>
     2 using namespace std;
     3 const int INF=2000000000;
     4 int main()
     5 {
     6     int n,x;
     7     cin>>n;
     8     int high=INF,low=-INF;//取临界值
     9     for(int i=0; i<n; i++)
    10     {
    11         char s[5]= {},t[5];
    12         scanf("%s%d%s",s,&x,t);
    13         if(t[0]=='N')
    14         {
    15             s[1]^='=';
    16             s[0]^='<'^'>';
    17         }//如果是N的话则把它取反
    18         if(s==string(">")) low=max(low,x+1);//前面用char后面得强制转换一下
    19         if(s==string("<"))  high=min(high,x-1);
    20         if(s==string(">=")) low=max(low,x);
    21         if(s==string("<=")) high=min(high,x);
    22     }//大取大小取小
    23     if(low<=high) printf("%d
    ",low);
    24     else printf("Impossible
    ");
    25     return 0;
    26 }
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  • 原文地址:https://www.cnblogs.com/zhien-aa/p/5683028.html
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