docs: add unit tests for all GRAPH_GUIDE.md examples and format code

Co-authored-by: samueltardieu <44656+samueltardieu@users.noreply.github.com>

Author: Copilot

examples/graph-adjacency-list.rs

@@ -19,9 +19,8 @@ fn main() {
     .collect();
 
     // Define the successor function
-    let successors = |node: &&str| -> Vec<(&str, u32)> {
-        graph.get(node).cloned().unwrap_or_default()
-    };
+    let successors =
+        |node: &&str| -> Vec<(&str, u32)> { graph.get(node).cloned().unwrap_or_default() };
 
     // Find shortest path from A to E using Dijkstra's algorithm
     let result = dijkstra(&"A", successors, |&node| node == "E");
@@ -40,7 +39,7 @@ fn main() {
 
     // Find another path: A to D
     let result2 = dijkstra(&"A", successors, |&node| node == "D");
-    
+
     match result2 {
         Some((path, cost)) => {
             println!("\nShortest path from A to D:");

examples/graph-adjacency-matrix.rs

@@ -9,11 +9,11 @@ fn main() {
     // Represent nodes as indices (0=A, 1=B, 2=C, 3=D, 4=E)
     // None means no edge, Some(weight) means edge with that weight
     let adjacency_matrix: Vec<Vec<Option<u32>>> = vec![
-        vec![None, Some(4), Some(2), None, None],       // Node 0 (A)
-        vec![None, None, Some(1), Some(5), None],       // Node 1 (B)
-        vec![None, None, None, Some(8), Some(10)],      // Node 2 (C)
-        vec![None, None, None, None, Some(2)],          // Node 3 (D)
-        vec![None, None, None, None, None],             // Node 4 (E)
+        vec![None, Some(4), Some(2), None, None],  // Node 0 (A)
+        vec![None, None, Some(1), Some(5), None],  // Node 1 (B)
+        vec![None, None, None, Some(8), Some(10)], // Node 2 (C)
+        vec![None, None, None, None, Some(2)],     // Node 3 (D)
+        vec![None, None, None, None, None],        // Node 4 (E)
     ];
 
     let num_nodes = adjacency_matrix.len();
@@ -40,7 +40,7 @@ fn main() {
     match result {
         Some((path, cost)) => {
             let path_names: Vec<char> = path.iter().map(|&i| NODE_NAMES[i]).collect();
-            
+
             println!("Shortest path from A to E using A*:");
             println!("  Path (indices): {path:?}");
             println!("  Path (names): {path_names:?}");
@@ -54,11 +54,11 @@ fn main() {
 
     // Example 2: Find path from B (1) to E (4)
     let result2 = astar(&1, successors, heuristic, |&node| node == 4);
-    
+
     match result2 {
         Some((path, cost)) => {
             let path_names: Vec<char> = path.iter().map(|&i| NODE_NAMES[i]).collect();
-            
+
             println!("\nShortest path from B to E:");
             println!("  Path (indices): {path:?}");
             println!("  Path (names): {path_names:?}");

examples/graph-unweighted-bfs.rs

@@ -19,9 +19,7 @@ fn main() {
     .collect();
 
     // Successor function returns just neighbors (no costs)
-    let successors = |node: &&str| -> Vec<&str> {
-        graph.get(node).cloned().unwrap_or_default()
-    };
+    let successors = |node: &&str| -> Vec<&str> { graph.get(node).cloned().unwrap_or_default() };
 
     // Find shortest path from A to F using BFS
     let result = bfs(&"A", successors, |&node| node == "F");
@@ -38,7 +36,7 @@ fn main() {
 
     // Example 2: Find path from A to E
     let result2 = bfs(&"A", successors, |&node| node == "E");
-    
+
     match result2 {
         Some(path) => {
             println!("\nShortest path from A to E: {path:?}");