Add solution #863

Author: JoshCrozier

README.md

@@ -670,6 +670,7 @@
 860|[Lemonade Change](./0860-lemonade-change.js)|Easy|
 861|[Score After Flipping Matrix](./0861-score-after-flipping-matrix.js)|Medium|
 862|[Shortest Subarray with Sum at Least K](./0862-shortest-subarray-with-sum-at-least-k.js)|Hard|
+863|[All Nodes Distance K in Binary Tree](./0863-all-nodes-distance-k-in-binary-tree.js)|Medium|
 867|[Transpose Matrix](./0867-transpose-matrix.js)|Easy|
 868|[Binary Gap](./0868-binary-gap.js)|Easy|
 872|[Leaf-Similar Trees](./0872-leaf-similar-trees.js)|Easy|

solutions/0863-all-nodes-distance-k-in-binary-tree.js

@@ -0,0 +1,59 @@
+/**
+ * 863. All Nodes Distance K in Binary Tree
+ * https://leetcode.com/problems/all-nodes-distance-k-in-binary-tree/
+ * Difficulty: Medium
+ *
+ * Given the root of a binary tree, the value of a target node target, and an integer k, return an
+ * array of the values of all nodes that have a distance k from the target node.
+ *
+ * You can return the answer in any order.
+ */
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @param {TreeNode} target
+ * @param {number} k
+ * @return {number[]}
+ */
+var distanceK = function(root, target, k) {
+  const graph = new Map();
+  const result = [];
+
+  buildGraph(root, null);
+  findNodesAtDistance(target.val, 0, new Set());
+
+  return result;
+
+  function buildGraph(node, parent) {
+    if (!node) return;
+    if (parent) {
+      graph.set(node.val, graph.get(node.val) || new Set());
+      graph.get(node.val).add(parent.val);
+      graph.set(parent.val, graph.get(parent.val) || new Set());
+      graph.get(parent.val).add(node.val);
+    }
+    buildGraph(node.left, node);
+    buildGraph(node.right, node);
+  }
+
+  function findNodesAtDistance(currentVal, distance, visited) {
+    if (distance === k) {
+      result.push(currentVal);
+      return;
+    }
+    visited.add(currentVal);
+    const neighbors = graph.get(currentVal) || new Set();
+    for (const neighbor of neighbors) {
+      if (!visited.has(neighbor)) {
+        findNodesAtDistance(neighbor, distance + 1, visited);
+      }
+    }
+  }
+};