Create 1245-tree-diameter.js

Author: everthis

1245-tree-diameter.js

@@ -0,0 +1,38 @@
+/**
+ * @param {number[][]} edges
+ * @return {number}
+ */
+const treeDiameter = function (edges) {
+  const graph = {}
+  for (const [u, v] of edges) {
+    if (graph[u] == null) graph[u] = new Set()
+    if (graph[v] == null) graph[v] = new Set()
+    graph[u].add(v)
+    graph[v].add(u)
+  }
+
+  let res = 0
+
+  dfs(0, -1)
+
+  return res
+  
+  function dfs(node, parent) {
+    let first = 0, sec = 0
+
+    for(const nxt of (graph[node] || [])) {
+      if(nxt === parent) continue
+      const childNum = dfs(nxt, node)
+      if(childNum > first) {
+        sec = first
+        first = childNum
+      } else if(childNum > sec){
+        sec = childNum
+      }
+    }
+
+    const nodeNum = first + sec + 1
+    res = Math.max(res, nodeNum - 1)
+    return first + 1
+  }
+}