Create maximum-difference-between-node-and-ancestor.cpp

Author: kamyu104

C++/maximum-difference-between-node-and-ancestor.cpp

@@ -0,0 +1,58 @@
+// Time:  O(n)
+// Space: O(h)
+
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+
+// iterative stack solution
+class Solution {
+public:
+    int maxAncestorDiff(TreeNode* root) {
+        using NODE = tuple<TreeNode*, int, int>;
+        int result = 0;
+        vector<NODE> stack{{root, 0, numeric_limits<int>::max()}};
+        while (!stack.empty()) {
+            TreeNode *node; int mx, mn;
+            tie(node, mx, mn) = stack.back(); stack.pop_back();
+            if (!node) {
+                continue;
+            }
+            result = max(result, max(mx - node->val, node->val - mn));
+            mx = max(mx, node->val);
+            mn = min(mn, node->val);
+            stack.emplace_back(node->left, mx, mn);
+            stack.emplace_back(node->right, mx, mn);
+        }
+        return result;
+    }
+};
+
+// Time:  O(n)
+// Space: O(h)
+// recursive solution
+class Solution2 {
+public:
+    int maxAncestorDiff(TreeNode* root) {
+        return maxAncestorDiffHelper(root, 0, numeric_limits<int>::max());
+    }
+
+private:
+    int maxAncestorDiffHelper(TreeNode* node, int mx, int mn) {
+        if (!node) {
+            return 0;
+        }
+        int result = max(mx - node->val, node->val - mn);
+        mx = max(mx, node->val);
+        mn = min(mn, node->val);
+        result = max(result, maxAncestorDiffHelper(node->left, mx, mn));
+        result = max(result, maxAncestorDiffHelper(node->right, mx, mn));
+        return result;
+    }
+};