6. Kitchen Plates（枚举，暴力）

Problem - 6 - Codeforces

6. Kitchen Plates

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

You are given 5 different sizes of kitchen plates. Each plate is marked with a letter A, B, C, D, or E. You are given 55 statements comparing two different plates, you need to rearrange the plates from smallest size to biggest size.

For example: the sizes of these plates

Input

The input consist of 55 lines. In each line there will be 33 characters, the first and last character will be either A, B, C, D, or E and the middle character will be either > or < describing the comparison between two plates sizes. No two plates will be equal.

Output

The output consist of 5 characters, the sorted order of balls from smallest to biggest plate. Otherwise, if the statements are contradicting print impossible. If there are multiple answers, print any of them

Examples

input

Copy

D>B
A>D
E<C
A>B
B>C

output

Copy

ECBDA

input

Copy

B>E
A>B
E>A
C<B
D<B

output

Copy

impossible

题意简单，五个盘子根据给出的大小关系进行排序。这是一道拓扑排序的题目，但因为数据量小，使用next_permutation()直接枚举。

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define TL ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
int a[5],p[5],q[5],pos[5];
char s[100];
int main()
{
    TL;
    for(int i = 0;i < 5;i++)
    {
        cin >> s;
        p[i] = s[0] -'A';
        q[i] = s[2] -'A';
        if(s[1]=='<') swap(p[i],q[i]);
        a[i] = i + 1; 
    }
    do
    {
        int flag = 1;
        for (int i = 0; i < 5; i++)
        {
            pos[a[i]-1] = i;
        }
        for (int i = 0; i < 5; i++)
        {
            if(pos[p[i]] < pos[q[i]]) flag = 0;
        }
        if(flag)
        {
            for(int i = 0;i < 5;i++)
            {
                cout << char('A'+a[i]-1);
            }
            return 0;
        }
    } while (next_permutation(a,a+5));
    puts("impossible");
    return 0;
}