[mkwkw] WEEK 04 Solutions

maximum-depth-of-binary-tree/mkwkw.cpp

@@ -0,0 +1,53 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int maxDepth(TreeNode* root) {
+
+        //root가 비어있는 경우
+        if(root == nullptr)
+        {
+            return 0;
+        }
+
+        stack<TreeNode*> nodeStack;
+        stack<int> depthStack;
+        int maxDepth = 0;
+
+        nodeStack.push(root);
+        depthStack.push(1);
+
+        while(!nodeStack.empty())
+        {
+            TreeNode* rootNode = nodeStack.top(); //change root pointer
+            int rootDepth = depthStack.top();
+            maxDepth = max(maxDepth, rootDepth);
+            nodeStack.pop();
+            depthStack.pop();
+
+            //making max depth binary tree
+            if(rootNode->left != nullptr)
+            {
+                nodeStack.push(rootNode->left);
+                depthStack.push(rootDepth+1);
+            }
+
+            if(rootNode->right != nullptr)
+            {
+                nodeStack.push(rootNode->right);
+                depthStack.push(rootDepth+1);
+            }
+
+        }
+        return maxDepth;
+    }
+};

merge-two-sorted-lists/mkwkw.cpp

@@ -0,0 +1,39 @@
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+//풀이 참고하였음.
+class Solution {
+public:
+    ListNode* mergeTwoLists(ListNode* list1, ListNode* list2) { //list1, list2 다 포인터
+        ListNode mergedNode(-1); //mergedNode 객체 선언
+        ListNode* mergedNodeList = &mergedNode; //node: (merged 객체)의 (주소) (&merged)저장 (객체를 포인터에 넣기)
+
+        ListNode* l1 = list1; // 포인터 l1
+        ListNode* l2 = list2; // 포인터 l2
+
+        while (l1 != nullptr && l2 != nullptr) {
+            //l1, l2 둘 중에 head 값(->val) 값이 작은 것을 node->next에 연결
+            if (l1->val < l2->val) { // 포인터로 객체의 속성 참조(->)
+                mergedNodeList->next = l1;
+                l1 = l1->next;
+            } else {
+                mergedNodeList->next = l2;
+                l2 = l2->next;
+            }
+            mergedNodeList = mergedNodeList->next;
+        }
+
+        //남아있는 list를 node->next에 연결
+        mergedNodeList->next = (l1 != nullptr) ? l1 : l2;
+        //return the head of the merged linked list (mergeNode -1 다음 것을 가리키는 포인터 next)
+        return mergedNode.next;
+
+    }
+};