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 watchin
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 ?-?10 9 ?≤? x ?≤?10 9 . 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 ?-?2·10 9 ?≤? y ?≤?2·10 9 . If there are many answers, print any of them. If such value doesn't exist, print word " Impossible " (without the quotes).
Sample test(s)
input
4 >= 1 Y 55 N
output
17
input
2 > 100 Y
output
Impossible
题目大意:
猜数字,给出n个区间询问,然后同时给出该区间是否正确,然后求出任何符合上述区间要求的数字.
解法:
先将答案范围规定为: [l,r] ;其中 l = -2*10^9 r = 2*10^9
每次读入,更新一次上届和下届,l和r;
读入结束后,
l > r Impossible
l 输出一个区间内的数字即可
代码:
#include
#define INF 2000000000
int n;
int max(int a, int b) {
if (a > b) return(a);
return(b);
}
int min(int a, int b) {
if (a ') {
if (ch2 == '=')
l = max(x, l);
else
l = max(x+1, l);
}
if (ch1 == ' ') {
if (ch2 == '=')
r = min(r, x-1);
else
r = min(r, x);
}
if (ch1 == '
.
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