feat: prims basic implementation without PQ

package.json

@@ -14,10 +14,13 @@
         "typescript": "^4.7.4"
     },
     "scripts": {
-        "test": "jest DFSOnBST LRU LinearSearchList BinarySearchList TwoCrystalBalls BubbleSort DoublyLinkedList Queue Stack ArrayList MazeSolver QuickSort BTPreOrder BTInOrder BTPostOrder BTBFS CompareBinaryTrees DFSOnBST DFSGraphList Trie BFSGraphMatrix Map MinHeap",
+        "test": "jest PrimsList",
         "clear": "node ./scripts/clear.js",
         "prettier": "prettier --write ./src",
         "generate": "node ./scripts/generate.js",
-        "day": "echo src\\day2"
+        "day": "echo src/day4"
+    },
+    "devDependencies": {
+        "@swc-node/register": "^1.6.7"
     }
-}
+}

src/golden/PrimList.ts

@@ -0,0 +1,92 @@
+export default function prims(list: WeightedAdjacencyList): WeightedAdjacencyList | null {
+
+    // Prims algorithm :: minimum spanning tree
+    // What is a minimum spanning tree?
+    //  - Requires no cycles
+    //  - For it to technically be a minimum spanning tree, the graph requires
+    //  to be strongly connected
+    // 1. Select starting node,
+    // 2. put edges of current selected node into a list
+    // 3. select edge that is the lowest value and to a node we haven't seen yet
+    // 4. we need to insert the edge from current to new into our mst
+    // 5. the newly selected node becomes the current node,
+    // 6. repeate to step 2 until unvisited is empty or unreachable
+    // ...
+    // 8. $$
+
+    const visited: boolean[] = new Array(list.length).fill(false);
+    const mst: GraphEdge[][] = new Array(list.length).fill(null).map(() => []);
+
+    // 1.
+    visited[0] = true;
+    let current = 0;
+
+    const edges: [number, GraphEdge][] = [];
+
+    do {
+        // 2. put all dem edges in the list
+        for (const edgemeDaddy of list[current]) {
+            edges.push([current, edgemeDaddy]);
+        }
+
+        // 3. select edge that is the lowest value and to a node we haven't seen yet
+        let lowest = Infinity;
+        let lowestEdge: [number, GraphEdge | null] = [-1, null];
+        for (const edge of edges) {
+            if (visited[edge[1].to] === false && edge[1].weight < lowest) {
+                lowest = edge[1].weight;
+                lowestEdge = edge;
+            }
+        }
+
+        // 4. we need to insert the edge from current to new into our mst, set visited, and remove the potential edge
+        if (lowestEdge[1] !== null) {
+            mst[lowestEdge[0]].push(lowestEdge[1]);
+            mst[lowestEdge[1].to].push({to: lowestEdge[0], weight: lowestEdge[1].weight});
+            visited[lowestEdge[1].to] = true;
+            edges.splice(edges.indexOf(lowestEdge as [number, GraphEdge]), 1);
+        }
+
+        // 5. the newly selected node becomes the current node
+        current = lowestEdge[1]?.to || -1;
+
+    } while (visited.includes(false) && current >= 0);
+
+    return mst;
+}
+
+if (require.main === module) {
+    prims([
+        [ // 0
+            { to: 2, weight: 1 },
+            { to: 1, weight: 3 },
+        ],
+        [ // 1
+            { to: 0, weight: 3 },
+            { to: 4, weight: 1 },
+            { to: 3, weight: 3 },
+        ],
+        [// 2
+            { to: 0, weight: 1 },
+            { to: 3, weight: 7 },
+        ],
+        [ // 3
+            { to: 6, weight: 1 },
+            { to: 1, weight: 3 },
+            { to: 2, weight: 7 },
+        ],
+        [ // 4
+            { to: 1, weight: 1 },
+            { to: 5, weight: 2 },
+        ],
+        [ // 5
+            { to: 4, weight: 2 },
+            { to: 6, weight: 1 },
+        ],
+        [ // 6
+            { to: 5, weight: 1 },
+            { to: 3, weight: 1 },
+        ],
+    ]);
+}
+

tsconfig.json

@@ -7,12 +7,12 @@
         "resolveJsonModule": true,
         "noImplicitReturns": true,
         "esModuleInterop": true,
-        "target": "es6",
+        "target": "esnext",
         "module": "commonjs",
         "baseUrl": "src",
         "paths": {
             "@code/*": [
-                "day2/*"
+                "day4/*"
             ]
         }
     },
@@ -22,4 +22,4 @@
     "exclude": [
         "node_modules"
     ]
-}
+}