Closest Common Ancestors
Time Limit: 10 Seconds
Memory Limit: 32768 KB
Write a program that takes as input a rooted tree and a list of pairs of vertices.
For each pair (u,v) the program determines the closest common ancestor of u
and v in the tree. The closest common ancestor of two nodes u and v is the node
w that is an ancestor of both u and v and has the greatest depth in the tree.
A node can be its own ancestor (for example in Figure 1 the ancestors of node
2 are 2 and 5)
The data set starts with the tree description, in the form:
vertex:(nr_of_successors) successor1 successor2 ... successorn
where vertices are represented as integers from 1 to n. The tree description
is followed by a list of pairs of vertices, in the form:
(u v) (x y) ...
The input contents several data sets (at least one).
Note that white-spaces (tabs, spaces and line breaks) can be used freely in
For each common ancestor the program prints the ancestor and the number of pair
for which it is an ancestor. The results are printed on the standard output
on separate lines, in to the ascending order of the vertices, in the format:
For example, for the following tree:
the program input and output is:
5:(3) 1 4 2
(1,5) (1,4) (4,2)
Source: Southeastern Europe 2000