Add solution #2003

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,681 LeetCode solutions in JavaScript
+# 1,682 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1537,6 +1537,7 @@
 2000|[Reverse Prefix of Word](./solutions/2000-reverse-prefix-of-word.js)|Easy|
 2001|[Number of Pairs of Interchangeable Rectangles](./solutions/2001-number-of-pairs-of-interchangeable-rectangles.js)|Medium|
 2002|[Maximum Product of the Length of Two Palindromic Subsequences](./solutions/2002-maximum-product-of-the-length-of-two-palindromic-subsequences.js)|Medium|
+2003|[Smallest Missing Genetic Value in Each Subtree](./solutions/2003-smallest-missing-genetic-value-in-each-subtree.js)|Hard|
 2011|[Final Value of Variable After Performing Operations](./solutions/2011-final-value-of-variable-after-performing-operations.js)|Easy|
 2016|[Maximum Difference Between Increasing Elements](./solutions/2016-maximum-difference-between-increasing-elements.js)|Easy|
 2017|[Grid Game](./solutions/2017-grid-game.js)|Medium|

solutions/2003-smallest-missing-genetic-value-in-each-subtree.js

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+/**
+ * 2003. Smallest Missing Genetic Value in Each Subtree
+ * https://leetcode.com/problems/smallest-missing-genetic-value-in-each-subtree/
+ * Difficulty: Hard
+ *
+ * There is a family tree rooted at 0 consisting of n nodes numbered 0 to n - 1. You are given a
+ * 0-indexed integer array parents, where parents[i] is the parent for node i. Since node 0 is
+ * the root, parents[0] == -1.
+ *
+ * There are 105 genetic values, each represented by an integer in the inclusive range [1, 105].
+ * You are given a 0-indexed integer array nums, where nums[i] is a distinct genetic value for
+ * node i.
+ *
+ * Return an array ans of length n where ans[i] is the smallest genetic value that is missing
+ * from the subtree rooted at node i.
+ *
+ * The subtree rooted at a node x contains node x and all of its descendant nodes.
+ */
+
+/**
+ * @param {number[]} parents
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var smallestMissingValueSubtree = function(parents, nums) {
+  const n = parents.length;
+  const result = new Array(n).fill(1);
+  const children = Array.from({ length: n }, () => []);
+  const seen = new Set();
+  let maxMissing = 1;
+
+  for (let i = 1; i < n; i++) {
+    children[parents[i]].push(i);
+  }
+
+  const nodeWithOne = nums.indexOf(1);
+  if (nodeWithOne === -1) return result;
+
+  let current = nodeWithOne;
+  while (current !== -1) {
+    const stack = [current];
+    while (stack.length) {
+      const node = stack.pop();
+      seen.add(nums[node]);
+      for (const child of children[node]) {
+        if (!seen.has(nums[child])) stack.push(child);
+      }
+    }
+    while (seen.has(maxMissing)) maxMissing++;
+    result[current] = maxMissing;
+    current = parents[current];
+  }
+
+  return result;
+};