first

Author: nimaipatel

algorithms/prims-algorithm/prims.c

@@ -11,31 +11,19 @@ typedef struct {
 	int a, b;
 } Pair;
 
-/*
- * returns cost of edge formed by vertices `i` and `j` in
- * graph represented by adjacency matrix `matrix`
- */
 double
 cost(Matrix * matrix, int i, int j)
 {
 	return matrix->arr[i * matrix->n_vertices + j];
 }
 
-/*
- * sets cost to `cost` between vertices `i` and `j` of
- * graph `matrix`
- */
 void
 set_cost(Matrix *matrix, int i, int j, double cost)
 {
 	matrix->arr[i * matrix->n_vertices + j] =
 		matrix->arr[j * matrix->n_vertices + i] = cost;
 }
 
-/*
- * creates matrix with `n` rows and columns to represent graph with
- * `n` nodes and initializes all edges to infinity i.e. not edges
- */
 Matrix *
 create_matrix(int n_vertices)
 {
@@ -48,15 +36,13 @@ create_matrix(int n_vertices)
 	return matrix;
 }
 
-/* destructor for matrix created with `create_matrix` */
 void
 destroy_matrix(Matrix *matrix)
 {
 	free(matrix->arr);
 	free(matrix);
 }
 
-/* gets edge with minimum cost from the graph */
 Pair
 get_min_cost_edge(Matrix * matrix)
 {
@@ -73,7 +59,6 @@ get_min_cost_edge(Matrix * matrix)
 	return min;
 }
 
-/* function to print square matrix */
 void 
 print_matrix(Matrix *matrix)
 {
@@ -85,10 +70,6 @@ print_matrix(Matrix *matrix)
 	}
 }
 
-/*
- * function accepts a graph represented by adjacency matrix `matrix`
- * and returns its MST's adjacency matrix
- */
 Matrix *
 prims_algorithm(Matrix *matrix)
 {
@@ -105,12 +86,7 @@ prims_algorithm(Matrix *matrix)
 			near[i] = k;
 	}
 	printf("\n");
-	/* we represent including `k` and `l` in MST by
-	 * setting their keys in `near` to -1 */
 	near[k] = near[l] = -1;
-	/* adjaceny matrix will have `n_vertices - 1` edges
-	 * we have filled one edge so loop has to run 
-	 * `n_vertices - 2` times */
 	for (int _ = 1; _ <= matrix->n_vertices - 2; ++_) {
 		int index;
 		double min_cost = INFINITY;
@@ -136,14 +112,19 @@ int
 main()
 {
 	Matrix * matrix = create_matrix(6);
-	set_cost(matrix, 0, 1, 8);
+	set_cost(matrix, 0, 1, 3);
+	set_cost(matrix, 0, 3, 4);
 	set_cost(matrix, 0, 2, 1);
-	set_cost(matrix, 1, 2, 5);
-	set_cost(matrix, 1, 3, 2);
-	set_cost(matrix, 2, 4, 7);
-	set_cost(matrix, 3, 4, 2);
-	set_cost(matrix, 3, 5, 3);
-	set_cost(matrix, 4, 5, 15);
+
+	set_cost(matrix, 1, 3, 5);
+	set_cost(matrix, 1, 4, 3);
+
+	set_cost(matrix, 2, 3, 5);
+	set_cost(matrix, 2, 5, 3);
+
+	set_cost(matrix, 5, 3, 6);
+	set_cost(matrix, 5, 4, 2);
+
 	Matrix *MST = prims_algorithm(matrix);
 	print_matrix(matrix);
 	printf("\n");