feat: 124. Binary Tree Maximum Path Sum

Author: gwbaik9717

binary-tree-maximum-path-sum/gwbaik9717.js

@@ -0,0 +1,47 @@
+// Time complexity: O(n)
+// Space complexity: 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 maxPathSum = function (root) {
+  let answer = Number.MIN_SAFE_INTEGER;
+
+  const dfs = (current) => {
+    const candidates = [current.val];
+
+    if (current.left) {
+      dfs(current.left);
+      candidates.push(current.left.val + current.val);
+    }
+
+    if (current.right) {
+      dfs(current.right);
+      candidates.push(current.right.val + current.val);
+    }
+
+    // 현재 노드가 루트일 경우
+    if (current.left && current.right) {
+      answer = Math.max(
+        answer,
+        current.left.val + current.right.val + current.val
+      );
+    }
+
+    current.val = Math.max(...candidates);
+    answer = Math.max(answer, current.val);
+  };
+
+  dfs(root);
+
+  return answer;
+};