From 64e0ffc682de88d588472924ca42fc6c804daebd Mon Sep 17 00:00:00 2001
From: Joseph Ferano <joseph@ferano.io>
Date: Wed, 18 Jan 2023 17:33:33 +0700
Subject: [PATCH] WIP graph implementation

---
 TheAlgorithmDesignManual.org | 65 ++++++++++++++++++++++++++++++++++--
 1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/TheAlgorithmDesignManual.org b/TheAlgorithmDesignManual.org
index 44fb680..f2dbc9b 100644
--- a/TheAlgorithmDesignManual.org
+++ b/TheAlgorithmDesignManual.org
@@ -781,9 +781,70 @@ operations.
   Use linked lists instead, however it is harder to verify if a certain edge
   exists. This can be mitigated by collecting them in a BFS of DFS.
 
-#+begin_src C :includes stdio.h stdlib.h
-//TODO Copy graph implementation
+#+begin_src C :includes stdio.h stdlib.h stdbool.h
+#define MAXV 1000
+
+struct edgenode {
+    int y;
+    int weight;
+    struct edgenode *next;
+};
+
+struct graph {
+    struct edgenode *edges[MAXV+1];
+    int degree[MAXV+1];
+    int nvertices;
+    int nedges;
+    bool directed;
+};
+
+void initialize_graph(struct graph *g, bool directed) {
+    g->nvertices = 0;
+    g->nedges = 0;
+    g->directed = directed;
+    for (int i = 1; i <= MAXV; i++) g->degree[i] = 0;
+    for (int i = 1; i <= MAXV; i++) g->edges[i] = NULL;
+}
+
+// TODO: We have to read whether the graph is directed or not and
+// insert edges twice
+void insert_edge(struct graph *g, int x, int y) {
+    struct edgenode *p;
+    p  = malloc(sizeof(struct edgenode));
+    p->weight = 0;
+    p->y = y;
+    p->next = g->edges[x];
+
+    g->edges[x] = p;
+    g->degree[x]++;
+
+    if (g->directed == false) {
+        insert_edge(g, y, x);
+    }
+}
+
+void print_graph(struct graph *g) {
+    int i;
+    struct edgenode *p;
+
+    for (i = 0; i <= g->nvertices; i++) {
+        printf("V%d", i);
+        p = g->edges[i];
+        while (p != NULL) {
+            printf("->%d", p->y);
+            p = p->next;
+        }
+        printf("\n");
+    }
+}
+
+struct graph *g = malloc(sizeof(struct graph));
+initialize_graph(g, true);
+print_graph(g);
 #+end_src
 
+#+RESULTS:
+: V0
+
 ** 5.3 War Story