Add BFS in C

06_breadth-first_search/c/01_breadth_first_search.c

@@ -0,0 +1,133 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct GraphNode {
+  char *key;
+  char **values;
+} GraphNode;
+
+GraphNode graph[] = {
+    {"you", (char *[]){"alice", "bob", "claire", NULL}},
+    {"bob", (char *[]){"anuj", "peggy", NULL}},
+    {"alice", (char *[]){"peggy", NULL}},
+    {"claire", (char *[]){"thom", "jonny", NULL}},
+    {"anuj", NULL},
+    {"peggy", NULL},
+    {"thom", NULL},
+    {"jonny", NULL},
+};
+
+typedef struct QueueNode {
+  char *name;
+  struct QueueNode *next;
+} QueueNode;
+
+typedef struct Queue {
+  struct QueueNode *head;
+  struct QueueNode *tail;
+} Queue;
+
+void enqueue(Queue *queue, char *name) {
+  QueueNode *node = (QueueNode *)malloc(sizeof(QueueNode));
+  node->name = name;
+  node->next = NULL;
+  if (queue->tail) {
+    queue->tail->next = node;
+    queue->tail = node;
+  } else {
+    queue->head = queue->tail = node;
+  }
+}
+
+char *dequeue(Queue *queue) {
+  if (!queue->head)
+    return NULL;
+  QueueNode *node = queue->head;
+  char *name = node->name;
+  queue->head = queue->head->next;
+  if (!queue->head)
+    queue->tail = NULL;
+  free(node);
+  return name;
+}
+
+int queue_empty(Queue *queue) { return queue->head == NULL; }
+
+void free_queue(Queue *queue) {
+  while (queue->head) {
+    QueueNode *node = queue->head;
+    queue->head = queue->head->next;
+    free(node);
+  }
+  queue->tail = NULL;
+}
+
+char **get_neighbors(char *name) {
+  for (int i = 0; i < sizeof(graph) / sizeof(graph[0]); i++) {
+    if (strcmp(graph[i].key, name) == 0) {
+      return graph[i].values;
+    }
+  }
+  return NULL;
+}
+
+int person_is_seller(char *name) {
+  int len = strlen(name);
+  return len > 0 && name[len - 1] == 'm';
+}
+
+int contains(char **list, int count, char *name) {
+  for (int i = 0; i < count; i++) {
+    if (strcmp(list[i], name) == 0) {
+      return 1;
+    }
+  }
+  return 0;
+}
+
+int search(char *name) {
+  Queue queue = {NULL, NULL};
+  char **neighbors = get_neighbors(name);
+  if (neighbors) {
+    for (int i = 0; neighbors[i]; i++) {
+      enqueue(&queue, neighbors[i]);
+    }
+  }
+
+  char **searched = NULL;
+  int searched_count = 0;
+  int searched_cap = 0;
+
+  int found = 0;
+  while (!queue_empty(&queue)) {
+    char *person = dequeue(&queue);
+    if (!contains(searched, searched_count, person)) {
+      if (person_is_seller(person)) {
+        printf("%s is a mango seller\n", person);
+        found = 1;
+        break;
+      }
+      char **neighbors = get_neighbors(person);
+      if (neighbors) {
+        for (int i = 0; neighbors[i]; i++) {
+          enqueue(&queue, neighbors[i]);
+        }
+      }
+      if (searched_count >= searched_cap) {
+        searched_cap = searched_cap ? searched_cap * 2 : 4;
+        searched = realloc(searched, searched_cap * sizeof(char *));
+      }
+      searched[searched_count++] = person;
+    }
+  }
+
+  free_queue(&queue);
+  free(searched);
+  return found;
+}
+
+int main() {
+  search("you");
+  return 0;
+}