Largest Color Value in a Directed Graph problem solved

Author: hasibulislam999

Easy/1857_largest-color-value-in-a-directed-graph.js

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+/**
+ * Title: Largest Color Value in a Directed Graph
+ * Description: There is a directed graph of n colored nodes and m edges. The nodes are numbered from 0 to n - 1.
+ * Author: Hasibul Islam
+ * Date: 10/04/2023
+ */
+
+/**
+ * @param {string} colors
+ * @param {number[][]} edges
+ * @return {number}
+ */
+const initializeGraph = (n) => {
+  let G = [];
+  for (let i = 0; i < n; i++) {
+    G.push([]);
+  }
+  return G;
+};
+const packDGDegree = (G, Edges, Deg) => {
+  for (const [u, v] of Edges) {
+    G[u].push(v);
+    Deg[v]++;
+  }
+}; // generate direct graph with indegree
+
+const largestPathValue = (colors, edges) => {
+  let n = colors.length,
+    m = edges.length,
+    indegree = Array(n).fill(0);
+  let g = initializeGraph(n);
+  packDGDegree(g, edges, indegree);
+  let order = topologicalSort(g, indegree);
+  if (order.length == 0) return -1;
+  let res = 0;
+  for (let x = 97; x <= 122; x++) {
+    let c = String.fromCharCode(x),
+      dp = Array(n).fill(0);
+    for (let i = 0; i < n; i++) {
+      let cur = order[i];
+      if (colors[cur] == c) dp[cur]++;
+      res = Math.max(res, dp[cur]);
+      for (const child of g[cur]) dp[child] = Math.max(dp[child], dp[cur]);
+    }
+  }
+  return res;
+};
+
+const topologicalSort = (g, indegree) => {
+  let res = [],
+    q = [],
+    n = g.length;
+  for (let i = 0; i < n; i++) {
+    // all nodes with no incoming edges
+    if (indegree[i] == 0) q.push(i);
+  }
+  while (q.length) {
+    let cur = q.shift();
+    res.push(cur);
+    for (const child of g[cur]) {
+      indegree[child]--; // remove an edge from cur to child
+      if (indegree[child] == 0) q.push(child); // child has no other incoming edges, add to q for next bfs
+    }
+  }
+  for (let i = 0; i < n; i++) {
+    if (indegree[i] > 0) return [];
+  }
+  return res;
+};