{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

notes66

# notes66 - Topological Sort It is a sorting of the vertices...

This preview shows pages 1–4. Sign up to view the full content.

Topological Sort It is a sorting of the vertices such that if there is an edge (i,j) then i should appear in the sorting before j Topological Sort: A,B,C,D,E,F or A,C,B,D,E,F Not a topological sort: C,E,A,B,D,F. (A doesn't appear before C) A topological sort is useful for scheduling of events that depend on each other. Example of using topological sort: A schedule of execution, such as for building a house Topological Sort 1. Foundation 2. Grass 3. Walls

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
4. Electric 5. Piping 6. Windows 7. End Algorithm: Topological Sorting Input: A diagraph G with n vertices Output: An array “sorted” with the vertices in topological order. // We use a stack to store the vertices with no dependencies stack{}; //Compute indegree of vertices for each edge(v,w){ // v->w indegree[w]++; } //Put vertices without incident edges (no dependencies) in stack for all u in G do if indegree[v] == 0 push v in stack; end end i=0; //index of "sorted" while stack is not empty u <- stack.pop() //u has no dependencies: add to "sorted" sorted[i] = u; i++; for all outgoing edges (u,w) of u do{ //remove dependency of u on w indegree[w]--; if indegree[w] == 0){ push w into stack; end end end if ( i < n ) { //not all vertices are sorted return null //topological sort not possible } return sorted Graphs with cycles do not have a topological sort! Class Graph{ int [] topoSort(){ //return an array with the vertices sorted topologically int [] indegree = new int[n]; //computer indegree for(int I = 0; I < n; i++){ for( int j = 0; j < n; j++){ if(adjacent[i][j]){ indegree[j]++; } } }
//initialize stack to keep track of vertices with indegree of 0 int[]

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 7

notes66 - Topological Sort It is a sorting of the vertices...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online