commit 268daf6c9359a0b1fa0bee54bf73d965068e1e17
Author: cy <hi@cything.io>
Date:   Mon Jan 13 22:49:04 2025 -0500

    implement graph

diff --git a/.gitignore b/.gitignore
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--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/Cargo.lock b/Cargo.lock
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index 0000000..d34ca04
--- /dev/null
+++ b/Cargo.lock
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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "skiena"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
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--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "skiena"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/src/graph.rs b/src/graph.rs
new file mode 100644
index 0000000..4998b11
--- /dev/null
+++ b/src/graph.rs
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+use std::rc::Rc;
+
+const MAXV: usize = 1000;
+
+#[derive(Clone)]
+struct Edgenode {
+    #[allow(unused)]
+    weight: i32, // Edge weight, if any
+
+    y: i32,                     // Adjacency info
+    next: Option<Rc<Edgenode>>, // next edge in list
+}
+
+pub struct Graph {
+    edges: Vec<Option<Rc<Edgenode>>>, // adjacency info
+    degree: Vec<i32>,                 // outdegree of each vertex
+    nvertices: i32,                   // number of vertices in graph
+    nedges: i32,                      // number of edges in graph
+    directed: bool,                   // is the graph directed?
+}
+
+impl Graph {
+    pub fn new(directed: bool) -> Self {
+        Self {
+            nvertices: 0,
+            nedges: 0,
+            directed,
+            degree: vec![0; MAXV],
+            edges: vec![None; MAXV],
+        }
+    }
+
+    fn insert_edge(&mut self, x: usize, y: i32, directed: bool) {
+        let p = Rc::new(Edgenode {
+            y,
+            weight: 0,
+            next: self.edges[x].clone(),
+        });
+        self.edges[x] = Some(p);
+        self.degree[x] += 1;
+        if directed {
+            self.nedges += 1;
+        } else {
+            self.insert_edge(y.try_into().unwrap(), x.try_into().unwrap(), true);
+        }
+    }
+
+    pub fn print_graph(&self) {
+        for i in 0..self.nvertices as usize {
+            print!("{} -->", i);
+            let mut p_opt = self.edges[i].clone();
+            while let Some(p) = p_opt {
+                print!(" {}", p.y);
+                p_opt = p.next.clone();
+            }
+            println!();
+        }
+    }
+
+    pub fn read_graph(&mut self, data: String) {
+        self._read_graph(data, self.directed);
+    }
+
+    fn _read_graph(&mut self, data: String, directed: bool) {
+        // reverse here so that we can pop() later
+        let mut data_parsed: Vec<&str> = data.split(' ').rev().collect();
+
+        // The first two digits in `data` are `nvertices` and the total number of edges
+        // between them
+        self.nvertices = data_parsed.pop().unwrap().parse().expect("invalid int");
+        let num_edges: i32 = data_parsed.pop().unwrap().parse().expect("invalid int");
+
+        // After that, parse edges as (x, y)
+        for _ in 0..num_edges {
+            let x: i32 = data_parsed.pop().unwrap().parse().unwrap();
+            let y: i32 = data_parsed.pop().unwrap().parse().unwrap();
+            self.insert_edge(x.try_into().unwrap(), y, directed);
+        }
+    }
+}
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..b4394c1
--- /dev/null
+++ b/src/main.rs
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+use crate::graph::Graph;
+
+mod graph;
+
+fn main() {
+    let mut graph = Graph::new(true);
+    let data = "5 14 \
+                1 2 \
+                1 5 \
+                2 1 \
+                2 5 \
+                2 3 \
+                2 4 \
+                3 2 \
+                3 4 \
+                4 2 \
+                4 5 \
+                4 3 \
+                5 4 \
+                5 1 \
+                5 2";
+    graph.read_graph(data.to_string());
+    graph.print_graph();
+}