exp 13: init

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

13.c

@@ -0,0 +1,136 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct Node node;
+struct Node {
+  int vertex;
+  struct Node *next;
+};
+
+typedef struct List list;
+struct List {
+  node *head;
+  node *tail;
+};
+
+typedef struct Graph graph;
+struct Graph {
+  int nvertices;
+  int *visited;
+  list *vertices;
+};
+
+graph *init_graph(int n) {
+  graph *graph = malloc(sizeof(struct Graph));
+
+  graph->nvertices = n;
+  graph->vertices = malloc(n * sizeof(struct List));
+  graph->visited = malloc(n * sizeof(int));
+
+  memset(graph->visited, 0, sizeof(int) * n);
+
+  return graph;
+}
+
+void insert(list *list, int vertex) {
+  node *new = malloc(sizeof(struct Node));
+  new->next = NULL;
+  new->vertex = vertex;
+
+  if (!list->head)
+    list->head = list->tail = new;
+  else
+    list->tail->next = new, list->tail = new;
+}
+
+void pop(list *list) {
+  if (!list->head)
+    return;
+
+  node *next = list->head->next;
+  free(list->head);
+
+  if (!next)
+    list->tail = next;
+  list->head = next;
+}
+
+void add_edge(graph *graph, int src, int dst) {
+  insert(&graph->vertices[src], dst);
+  insert(&graph->vertices[dst], src);
+}
+
+void dfs(struct Graph *graph, int vertex) {
+  list list = graph->vertices[vertex];
+
+  printf("%d ", vertex);
+  graph->visited[vertex] = 1;
+
+  node *cur = list.head;
+
+  while (cur) {
+    if (!graph->visited[cur->vertex])
+      dfs(graph, cur->vertex);
+
+    cur = cur->next;
+  }
+}
+
+void bfs(struct Graph *graph, int _vertex) {
+  list next;
+  next.head = next.tail = NULL;
+
+  graph->visited[_vertex] = 1;
+  insert(&next, _vertex);
+
+  while (next.head) {
+    int vertex = next.head->vertex;
+    list list = graph->vertices[vertex];
+    node *cur = list.head;
+
+    printf("%d ", vertex);
+    pop(&next);
+
+    while (cur) {
+      if (!graph->visited[cur->vertex]) {
+        graph->visited[cur->vertex] = 1;
+        insert(&next, cur->vertex);
+      }
+
+      cur = cur->next;
+    }
+  }
+}
+
+int main() {
+  const int ROOT = 0;
+  const int SIZE = 5;
+
+  struct Graph *graph = init_graph(SIZE);
+  add_edge(graph, 0, 1);
+  add_edge(graph, 0, 3);
+  add_edge(graph, 0, 4);
+  add_edge(graph, 2, 3);
+  add_edge(graph, 1, 3);
+
+  printf("DFS: ");
+  dfs(graph, ROOT);
+  printf("\n");
+
+  memset(graph->visited, 0, sizeof(int) * graph->nvertices);
+
+  printf("BFS: ");
+  bfs(graph, ROOT);
+  printf("\n");
+
+  // free
+  for (int i = 0; i < graph->nvertices; i++)
+    while(graph->vertices[i].head)
+      pop(&graph->vertices[i]);
+  free(graph->visited);
+  free(graph->vertices);
+  free(graph);
+
+  return 0;
+}