Laboratory Exercises, C++ Programming

22 Tools for Practical C++ Development
The algorithm should detect cycles in the graph. If that happens, your function should throw
a cyclic exception. The cycle detection is not described in the algorithm; you must add that
yourself.
Topological-Sort(Graph G) {
/* 1. initialize the graph and the result stack */
for each vertex v in G
v.color = WHITE;
Stack result;
/* 2. search from all unvisited vertices */
for each vertex v in G
if (v.color == WHITE)
DFS-visit(v, result);
}
DFS-visit(Vertex v, Stack result) {
/* 1. white vertex v is just discovered, color it gray */
v.color = GRAY;
/* 2. recursively visit all unvisited adjacent nodes */
for each vertex w in v.adj
if (w.color == WHITE)
DFS-visit(w);
/* 3. finish vertex v (color it black and output it) */
v.color = BLACK;
result.push(v.name);
}
A8. Implement top sort and dfs visit and test the program.
4.4 Parsing the Makefile
A9. Finally, you are ready to solve the last part of the assignment: to read a makefile, build a
graph, sort it topologically and print the results. The input to the program is a makefile
containing lines of the type:
target: prereq1 prereq2 ...
The names of the target and the prerequisites are strings. The list of prerequisites may
be empty. The program should perform reasonable syntax checks (the most important is
probably that a line must contain a target).
The file topsort.cc contains a test program. Implement the function buildGraph and
test. The files test[1-5].txt contain test cases (the same that were used in the graph test
program in assignment A8), but you are encouraged to also test other cases.