From 8de4107b9594c61c1b04be91e52c40bce20ebeff Mon Sep 17 00:00:00 2001
From: Yanick Champoux <yanick@babyl.ca>
Date: Sun, 12 Dec 2021 13:19:18 -0500
Subject: [PATCH] part 2

---
 2021/12/part1.mjs | 51 ++++++++++++++++++++++++++++++++++++++
 2021/12/part2.mjs | 63 +++++++++++++++++++++++++++++++++++++++++++++++
 2021/12/sample    |  7 ++++++
 2021/12/test.mjs  | 20 +++++++++++++++
 4 files changed, 141 insertions(+)
 create mode 100644 2021/12/part1.mjs
 create mode 100644 2021/12/part2.mjs
 create mode 100644 2021/12/sample
 create mode 100644 2021/12/test.mjs

diff --git a/2021/12/part1.mjs b/2021/12/part1.mjs
new file mode 100644
index 0000000..8767932
--- /dev/null
+++ b/2021/12/part1.mjs
@@ -0,0 +1,51 @@
+import fs from "fs-extra";
+import fp from "lodash/fp.js";
+import _ from "lodash";
+
+import Graph from 'graphology';
+
+
+
+export const processInput = (filename) => fs.readFile(filename,'utf8').then(
+    content => content.split("\n").filter(x=>x)
+).then(
+    lines => {
+        const graph = new Graph();
+        lines.map( line => line.split('-') ).forEach( edge =>
+            graph.mergeEdge(...edge) );
+        return graph;
+    }
+
+);
+
+export function solution(graph) {
+    let paths = 0;
+    const left = [
+        { graph, where: 'start' }
+    ];
+
+    while( left.length > 0 ) {
+        const position = left.shift();
+
+        if( position.where === 'end' ) {
+            paths++;
+            continue;
+        }
+
+        let newGraph = position.graph;
+        if( position.where === position.where.toLowerCase()  ) {
+            newGraph = position.graph.copy();
+            newGraph.dropNode(position.where);
+        }
+
+        for( const n of position.graph.neighbors(position.where) ) {
+            left.unshift({
+                graph: newGraph,
+                where: n,
+            });
+        }
+
+    }
+
+    return paths;
+}
diff --git a/2021/12/part2.mjs b/2021/12/part2.mjs
new file mode 100644
index 0000000..eaf12ba
--- /dev/null
+++ b/2021/12/part2.mjs
@@ -0,0 +1,63 @@
+import fs from "fs-extra";
+import fp from "lodash/fp.js";
+import _ from "lodash";
+
+import * as p1 from './part1.mjs';
+
+export function solution(graph) {
+    let paths = 0;
+
+    graph.forEachNode( node => {
+        graph.setNodeAttribute( node, 'nbrVisits', 0 )
+    } );
+
+    const left = [
+        { graph, where: 'start' }
+    ];
+
+    while( left.length > 0 ) {
+        const position = left.shift();
+
+        if( position.where === 'end' ) {
+            paths++;
+            continue;
+        }
+
+        const canVisit = (graph,node) => {
+            if(node === 'start') return false;
+            if( node === node.toUpperCase() ) return true;
+            const nbrVisits =graph.getNodeAttribute(node,'nbrVisits');
+
+            if(nbrVisits ===0  ) return true;
+            if(nbrVisits>1) return false;
+            return !graph.hasAttribute('revisited');
+        }
+
+        for( const n of position.graph.neighbors(position.where) ) {
+            if( !canVisit( position.graph, n ) ) continue;
+
+            let newGraph = position.graph;
+
+            if( n === n.toLowerCase() ) {
+                newGraph = newGraph.copy();
+                newGraph.setNodeAttribute(
+                    n, 'nbrVisits', 1 + newGraph.getNodeAttribute(n,'nbrVisits')
+                );
+
+
+                if( newGraph.getNodeAttribute(n,'nbrVisits') === 2 ) {
+                    newGraph.setAttribute('revisited',n);
+                }
+
+            }
+
+            left.unshift({
+                graph: newGraph,
+                where: n,
+            });
+        }
+
+    }
+
+    return paths;
+}
diff --git a/2021/12/sample b/2021/12/sample
new file mode 100644
index 0000000..6fd8c41
--- /dev/null
+++ b/2021/12/sample
@@ -0,0 +1,7 @@
+start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end
diff --git a/2021/12/test.mjs b/2021/12/test.mjs
new file mode 100644
index 0000000..196547b
--- /dev/null
+++ b/2021/12/test.mjs
@@ -0,0 +1,20 @@
+// https://adventofcode.com/2021/day/12
+
+import tap from "tap";
+import fs from "fs-extra";
+
+import * as p1 from "./part1.mjs";
+import * as p2 from "./part2.mjs";
+
+const sample = p1.processInput('sample');
+const input = p1.processInput('input');
+
+tap.test("part1", async (t) => {
+    t.equal(p1.solution(await sample), 10);
+    t.equal(p1.solution(await input), 3450);
+});
+
+tap.test("part2", async (t) => {
+    t.equal(p2.solution(await sample), 36);
+    t.equal(p2.solution(await input), 96528);
+});