feat: add deikstra algorithm

Author: soloVlad

deikstra/deikstra.js

@@ -0,0 +1,77 @@
+const graph = {
+  'start': {
+    'a': 6,
+    'b': 2
+  },
+  'a': {
+    'finish': 1
+  },
+  'b': {
+    'a': 3,
+    'finish': 5
+  },
+  'finish': {}
+};
+
+const costs = {
+  'a': 6,
+  'b': 2,
+  'finish': Infinity
+};
+
+const parents = {
+  'a': 'start',
+  'b': 'start',
+  'finish': null
+};
+
+const processed = [];
+
+
+let node = findLowestCostNode(costs, processed);
+while (node) {
+  const cost = costs[node];
+  const neighbors = graph[node];
+
+  for (const [neighbor, neighborCost] of Object.entries(neighbors)) {
+    const newCost = cost + neighborCost;
+    if (newCost < costs[neighbor]) {
+      costs[neighbor] = newCost;
+      parents[neighbor] = node;
+    }
+  }
+  processed.push(node);
+  node = findLowestCostNode(costs, processed);
+}
+
+
+console.log(costs['finish']);
+const shortestPath = restoreShortestPath(parents);
+console.log(shortestPath.join(' <- '));
+
+
+function findLowestCostNode(costs, processed) {
+  let lowestCost = Infinity;
+  let lowestCostNode = null;
+  for (const [node, cost] of Object.entries(costs)) {
+    if (processed.includes(node)) continue;
+    if (cost < lowestCost) {
+      lowestCost = cost;
+      lowestCostNode = node;
+    }
+  }
+
+  return lowestCostNode;
+}
+
+function restoreShortestPath(parents) {
+  let startNode = 'finish';
+  const path = [startNode];
+  while (startNode !== 'start') {
+    const parent = parents[startNode];
+    path.push(parent);
+    startNode = parent;
+  }
+
+  return path;
+}