Merge pull request #552 from JEONGHWANMIN/main

[환미니니] Week11 Solutions

Author: SamTheKorean

graph-valid-tree/hwanmini.js

@@ -0,0 +1,45 @@
+// V: Node 개수, E: 간선의 개수
+// 시간복잡도: O(V + E)
+// 공간복잡도: O(V + E)
+
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @returns {boolean}
+     */
+    validTree(n, edges) {
+        const graph = new Map();
+
+        for (let [u, v] of edges) {
+            if (!graph.has(u)) graph.set(u, [])
+            if (!graph.has(v)) graph.set(v, [])
+            graph.get(u).push(v)
+            graph.get(v).push(u)
+        }
+
+        const visited = Array.from({length: n}, () => false);
+
+        let edgeCount = 0;
+        const queue = [0];
+        visited[0] = true
+
+        while(queue.length) {
+            const cur = queue.shift();
+
+            for (const edge of graph.get(cur) || []) {
+                if (!visited[edge]) {
+                    visited[edge] = true;
+                    queue.push(edge)
+                }
+                edgeCount++;
+            }
+        }
+
+        const isAllVisited = visited.every((visited) => visited === true)
+
+        return isAllVisited && (edgeCount / 2) === (n - 1)
+    }
+
+
+}

maximum-depth-of-binary-tree/hwanmini.js

@@ -0,0 +1,34 @@
+// 시간복잡도: O(n)
+// 공간복잡도: O(n)
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number}
+ */
+var maxDepth = function(root) {
+    if (!root) return 0;
+
+    let maxDepth = 0;
+    const exploreMaxDepth = (node, depth) => {
+        if (!node) {
+            maxDepth = Math.max(maxDepth, depth)
+            return
+        }
+
+
+        exploreMaxDepth(node.left, depth + 1)
+        exploreMaxDepth(node.right, depth + 1)
+    }
+
+    exploreMaxDepth(root, 0)
+
+    return maxDepth
+};