134 lines
3.6 KiB
Dart
134 lines
3.6 KiB
Dart
/**
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* File: graph_adjacency_matrix.dart
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* Created Time: 2023-05-15
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* Author: liuyuxin (gvenusleo@gmail.com)
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*/
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import '../utils/print_util.dart';
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/* Undirected graph class based on adjacency matrix */
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class GraphAdjMat {
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List<int> vertices = []; // Vertex element, element represents "vertex value", index represents "vertex index"
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List<List<int>> adjMat = []; //Adjacency matrix, row and column indices correspond to "vertex index"
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/* Constructor */
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GraphAdjMat(List<int> vertices, List<List<int>> edges) {
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this.vertices = [];
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this.adjMat = [];
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// Add vertex
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for (int val in vertices) {
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addVertex(val);
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}
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// Add edge
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// Please note, edges elements represent vertex indices, corresponding to vertices elements indices
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for (List<int> e in edges) {
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addEdge(e[0], e[1]);
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}
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}
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/* Get the number of vertices */
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int size() {
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return vertices.length;
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}
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/* Add vertex */
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void addVertex(int val) {
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int n = size();
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// Add new vertex value to the vertex list
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vertices.add(val);
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// Add a row to the adjacency matrix
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List<int> newRow = List.filled(n, 0, growable: true);
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adjMat.add(newRow);
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// Add a column to the adjacency matrix
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for (List<int> row in adjMat) {
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row.add(0);
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}
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}
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/* Remove vertex */
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void removeVertex(int index) {
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if (index >= size()) {
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throw IndexError;
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}
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// Remove vertex at `index` from the vertex list
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vertices.removeAt(index);
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// Remove the row at `index` from the adjacency matrix
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adjMat.removeAt(index);
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// Remove the column at `index` from the adjacency matrix
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for (List<int> row in adjMat) {
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row.removeAt(index);
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}
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}
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/* Add edge */
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// Parameters i, j correspond to vertices element indices
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void addEdge(int i, int j) {
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// Handle index out of bounds and equality
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if (i < 0 || j < 0 || i >= size() || j >= size() || i == j) {
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throw IndexError;
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}
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// In an undirected graph, the adjacency matrix is symmetric about the main diagonal, i.e., satisfies (i, j) == (j, i)
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adjMat[i][j] = 1;
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adjMat[j][i] = 1;
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}
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/* Remove edge */
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// Parameters i, j correspond to vertices element indices
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void removeEdge(int i, int j) {
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// Handle index out of bounds and equality
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if (i < 0 || j < 0 || i >= size() || j >= size() || i == j) {
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throw IndexError;
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}
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adjMat[i][j] = 0;
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adjMat[j][i] = 0;
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}
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/* Print adjacency matrix */
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void printAdjMat() {
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print("Vertex list = $vertices");
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print("Adjacency matrix = ");
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printMatrix(adjMat);
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}
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}
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/* Driver Code */
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void main() {
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/* Initialize undirected graph */
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// Please note, edges elements represent vertex indices, corresponding to vertices elements indices
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List<int> vertices = [1, 3, 2, 5, 4];
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List<List<int>> edges = [
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[0, 1],
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[0, 3],
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[1, 2],
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[2, 3],
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[2, 4],
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[3, 4],
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];
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GraphAdjMat graph = GraphAdjMat(vertices, edges);
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print("\nAfter initialization, the graph is");
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graph.printAdjMat();
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/* Add edge */
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// Indices of vertices 1, 2 are 0, 2 respectively
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graph.addEdge(0, 2);
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print("\nAfter adding edge 1-2, the graph is");
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graph.printAdjMat();
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/* Remove edge */
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// Indices of vertices 1, 3 are 0, 1 respectively
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graph.removeEdge(0, 1);
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print("\nAfter removing edge 1-3, the graph is");
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graph.printAdjMat();
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/* Add vertex */
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graph.addVertex(6);
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print("\nAfter adding vertex 6, the graph is");
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graph.printAdjMat();
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/* Remove vertex */
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// Index of vertex 3 is 1
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graph.removeVertex(1);
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print("\nAfter removing vertex 3, the graph is");
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graph.printAdjMat();
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}
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