Merge pull request #2485 from sadie100/main

[sadie100] WEEK 04 Solutions

Author: sadie100

maximum-depth-of-binary-tree/sadie100.ts

@@ -0,0 +1,34 @@
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     val: number
+ *     left: TreeNode | null
+ *     right: TreeNode | null
+ *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.left = (left===undefined ? null : left)
+ *         this.right = (right===undefined ? null : right)
+ *     }
+ * }
+ */
+
+/*
+ DFS로 노드를 탐색해가며 최대깊이를 찾는다
+ 
+ 시간 복잡도 : O(N - binary tree의 깊이)
+
+ */
+
+function maxDepth(root: TreeNode | null): number {
+  let result = 0
+  const search = (node, floor) => {
+    if (!node) return
+    result = Math.max(floor, result)
+
+    search(node.left, floor + 1)
+    search(node.right, floor + 1)
+  }
+
+  search(root, 1)
+  return result
+}

merge-two-sorted-lists/sadie100.ts

@@ -0,0 +1,51 @@
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     val: number
+ *     next: ListNode | null
+ *     constructor(val?: number, next?: ListNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.next = (next===undefined ? null : next)
+ *     }
+ * }
+ */
+
+/*
+새 mergeList를 만들고 list1, list2를 순회하며 더 작은 값을 mergeList에 넣는다.
+두 리스트의 next가 비게 되면 mergeList의 head를 리턴한다.
+
+시간복잡도 : O(N+K) (N은 list1의 길이, K는 list2의 길이)
+
+*/
+
+function mergeTwoLists(
+  list1: ListNode | null,
+  list2: ListNode | null,
+): ListNode | null {
+  let now = null
+  let head = null
+
+  while (list1 || list2) {
+    if (!list2 || (list1 && list1.val <= list2.val)) {
+      if (!now) {
+        now = list1
+        head = now
+      } else {
+        now.next = list1
+        now = now.next
+      }
+      list1 = list1.next
+    } else {
+      if (!now) {
+        now = list2
+        head = now
+      } else {
+        now.next = list2
+        now = now.next
+      }
+      list2 = list2.next
+    }
+  }
+
+  return head
+}