Is-A? Has-A? Who Knowz-A?
Time limit2sMemory limit512 MB
Given is-a and has-a edges between classes, answer queries whether one class is-a or has-a another using inheritance and field transitivity.
- Level
Medium6 of 10
- Topics
- Graph, BFS, DFS, Bit manipulation
- Solved
- No attempts yet
Problem
Two familiar concepts in object oriented programming are the is-a and has-a relationships. Given two classes A and B, we say that A is-a B if A is a subclass of B; we say A has-a B if one of the fields of A is of type B. For example, we could imagine an object-oriented language (call it ICPC++) with code like that in Figure E.1, where the class Day is-a Time, the class Appointment is both a DateBook and a Reminder, and class Appointment has-a Day.
class Day extends Time class Appointment extends Datebook, Reminder
{ {
... private Day date;
} ...
}
Figure E.1: Two ICPC++ classes.
These two relationships are transitive. For example if A is-a B and B is-a C then it follows that A is-a C. This holds as well if we change all the is-a's in the last sentence to has-a's. It also works with combinations of is-a's and has-a's: in the example above, Appointment has-a Time, since it has-a Day and Day is-a Time. Similarly, if class DateBook has-a Year then Appointment has-a Year, since Appointment is-a DateBook.
In this problem you will be given a set of is-a and has-a relationships and a set of queries of the form A is/has-a B. You must determine if each query is true or false.
Input
Input starts with two integers n and m, (1 ≤ n, m ≤ 10, 000), where n specifies the number of given is-a and has-a relationships and m specifies the number of queries. The next n lines each contain one given relationship in the form c1 r c2 where c1 and c2 are single-word class names, and r is either the string “is-a” or “has-a”. Following this are m queries, one per line, using the same format. There will be at most 500 distinct class names in the n + m lines, and all class names in the last m lines will appear at least once in the initial n lines. All is-a and has-a relationships between the given classes can be deduced from the n given relationships. Is-a relationships can not be circular (apart from the trivial identity “x is-a x”).
Output
For each query, display the query number (starting at one) and whether the query is true or false.