834

Author: lazzzis

834/main.js

@@ -0,0 +1,47 @@
+/**
+ * @param {number} N
+ * @param {number[][]} edges
+ * @return {number[]}
+ */
+var sumOfDistancesInTree = function (N, edges) {
+  const conn = Array.from({length: N}, () => [])
+  const nodes = Array.from({length: N + 1}, () => ({}))
+  const disOfSubTree = Array.from({length: N + 1}, () => ({}))
+  for (const [a, b] of edges) {
+    conn[a].push(b)
+    conn[b].push(a)
+    nodes[a][b] = -1
+    nodes[b][a] = -1
+    disOfSubTree[a][b] = -1
+    disOfSubTree[b][a] = -1
+  }
+
+  function helper (cur, from) {
+    if (nodes[from][cur] != null && nodes[from][cur] !== -1) {
+      return {
+        dis: disOfSubTree[from][cur],
+        nodeCnt: nodes[from][cur]
+      }
+    }
+    nodes[from][cur] = 0
+    disOfSubTree[from][cur] = 0
+    for (const next of conn[cur]) {
+      if (next === from) {
+        continue
+      }
+      const {dis, nodeCnt} = helper(next, cur)
+      nodes[from][cur] += nodeCnt + 1
+      disOfSubTree[from][cur] += dis + 1 + nodeCnt
+    }
+    return {
+      dis: disOfSubTree[from][cur],
+      nodeCnt: nodes[from][cur]
+    }
+  }
+
+  const ans = []
+  for (let i = 0; i < N; i++) {
+    ans.push(helper(i, N).dis)
+  }
+  return ans
+}

README.md

@@ -249,6 +249,7 @@
 - [817 Linked List Components](./817/main.js)
 - [832 Flipping an Image](./832/main.js)
 - [833 Find And Replace in String](./833/main.js)
+- [834 Sum of Distances in Tree](./834/main.js)
 - [835 Image Overlap](./835/main.js)
 
 *Q: What is `LZS`? It almost appears inside all files (like js, cpp)?*