A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with several vertex sets, you are supposed to tell if each of them is a ve ...

There is a kind of balanced binary search tree named red-black tree in the data structure. It has the following 5 properties:(1) Every node is either red or black.(2) The root is black.(3) Every leaf (NULL) is black.(4) ...

In the big cities, the subway systems always look so complex to the visitors. To give you some sense, the following figure shows the map of Beijing subway. Now you are supposed to help people with your computer skills! Given the ...

Given a syntax tree (binary), you are supposed to output the corresponding infix expression, with parentheses reflecting the precedences of the operators.Input Specification:Each input file contains one test case. For each case, ...

The "eight queens puzzle" is the problem of placing eight chess queens on an 8×8 chessboard so that no two queens threaten each other. Thus, a solution requires that no two queens share the same row, column, o ...