Codeforces Round #290 (Div. 2) C. Fox And Names 拓扑排序
来源:互联网 发布:java代码编写经验 编辑:程序博客网 时间:2024/05/21 08:57
Fox Ciel is going to publish a paper on FOCS (Foxes Operated Computer Systems, pronounce: "Fox"). She heard a rumor: the authors list on the paper is always sorted in the lexicographical order.
After checking some examples, she found out that sometimes it wasn't true. On some papers authors' names weren't sorted inlexicographical order in normal sense. But it was always true that after some modification of the order of letters in alphabet, the order of authors becomes lexicographical!
She wants to know, if there exists an order of letters in Latin alphabet such that the names on the paper she is submitting are following in the lexicographical order. If so, you should find out any such order.
Lexicographical order is defined in following way. When we compare s and t, first we find the leftmost position with differing characters:si ≠ ti. If there is no such position (i. e. s is a prefix of t or vice versa) the shortest string is less. Otherwise, we compare characters si andti according to their order in alphabet.
The first line contains an integer n (1 ≤ n ≤ 100): number of names.
Each of the following n lines contain one string namei (1 ≤ |namei| ≤ 100), the i-th name. Each name contains only lowercase Latin letters. All names are different.
If there exists such order of letters that the given names are sorted lexicographically, output any such order as a permutation of characters 'a'–'z' (i. e. first output the first letter of the modified alphabet, then the second, and so on).
Otherwise output a single word "Impossible" (without quotes).
3rivestshamiradleman
bcdefghijklmnopqrsatuvwxyz
10touristpetrwjmzbmryeputonsvepifanovscottwuoooooooooooooooosubscriberrowdarktankengineer
Impossible
10petregorendagorionfeferivanilovetanyaromanovakostkadmitriyhmaratsnowbearbredorjaguarturnikcgyforever
aghjlnopefikdmbcqrstuvwxyz
7carcarecarefulcarefullybecarefuldontforgetsomethingotherwiseyouwillbehackedgoodluck
acbdefhijklmnogpqrstuvwxyz
题目给出一个字符串集,并假设是字典序的,要求26个字母的字典序(自定义的字典序),每两个字符串,可以得出一对字符的优先级,然后得出了所有字符的先后顺序,就转化成了拓扑排序的问题了,使用了优先队列,这样可以尽可能的小的在前面。其次,如果有ab a,这样的字符串,可以直接认为是不可能存在的!
#define N 105#define MOD 1000000000000000007struct node{ int x; node(int xx){ x = xx; } bool operator < (const node a) const{ return x>a.x; }};int n,in[30],ans[30],ansNum;char str[N][N];bool land[30][30];priority_queue<node> myqueue;bool getland(int x,int y){ int len = min(strlen(str[x]),strlen(str[y])); FI(len){ if(str[x][i] != str[y][i]){ land[str[x][i] - 'a'][str[y][i]-'a'] = true; return true; } } if(strlen(str[x])>strlen(str[y])) return false; return true;}int main(){ while(S(n)!=EOF) { FI(n){ SS(str[i]); } memset(land,false,sizeof(land)); bool flag = true; for(int i=0;i<n && flag;i++){ for(int j = i+1;j<n && flag;j++){ flag = getland(i,j); } } if(!flag){ printf("Impossible\n"); continue; } memset(in,0,sizeof(in)); FI(26){ FJ(26){ if(land[i][j]){ in[j]++; } } } while(!myqueue.empty()) myqueue.pop(); for(int i=0;i<26;i++){ if(in[i] == 0){ myqueue.push(node(i)); } } ansNum = 0; while(!myqueue.empty()){ node top = myqueue.top(); myqueue.pop(); ans[ansNum++] = top.x; FI(26){ if(land[top.x][i]){ in[i]--; if(in[i] == 0) myqueue.push(node(i)); } } } if(ansNum == 26){ FI(ansNum) printf("%c",ans[i]+'a'); printf("\n"); } else printf("Impossible\n"); } return 0;}
- Codeforces Round #290 (Div. 2)C. Fox And Names(拓扑排序)
- Codeforces Round #290 (Div. 2)C - Fox And Names——拓扑排序
- Codeforces Round #290 (Div. 2) C. Fox And Names 拓扑排序
- Codeforces Round #290 (Div. 2) C. Fox And Names 拓扑排序
- Codeforces Round #290 (Div. 2) C. Fox And Names 拓扑排序
- Codeforces Round #290 (Div. 2) - C. Fox And Names (拓扑排序)
- 拓扑排序——Codeforces Round #290 (Div. 2) C. Fox And Names
- C. Fox And Names Codeforces Round #290 (Div. 2)
- C. Fox And Names(Codeforces Round #290 (Div. 2))
- Codeforces Round #290 (Div. 2) C. Fox And Names
- Codeforces Round #290 (Div. 2) C题Fox And Names
- Codeforces Round #290 (Div. 2)-C. Fox And Names
- 【拓扑排序】 Codeforces Round #290 (Div. 1) A Fox And Names
- Codeforces Round #290 (Div. 2) C. Fox And Names && D. Fox And Jumping
- Codeforces Round #290 (Div. 2) - C. Fox And Names(最短路)
- codeforces 510C Fox And Names 拓扑排序
- Codeforces 510C - Fox And Names (拓扑排序)
- Codeforces 510C Fox And Names 拓扑排序
- TA们是这样描述"睿哥"的
- Python图像处理(15):SVM分类器
- 返回值为对象调用拷贝构造函数
- 经典排序算法
- LeetCode216:Combination Sum III
- Codeforces Round #290 (Div. 2) C. Fox And Names 拓扑排序
- 命令模式,状态模式和职责链模式的不同
- 【bzoj2510】弱题 概率dp+循环矩阵矩阵乘法
- STL之nth_element()(取容器中的第n大值)
- Android 进阶学习:Android LayoutInflater原理分析,带你一步步深入了解View(一)
- 开启博客之路
- 关于重载二义性
- 使用事件通道
- Java模板模式(Template模式)