add 1026

fishercoder1534 · fishercoder1534 · commit cf6edfd57825 · 2021-12-31T10:42:15.000-08:00
diff --git a/README.md b/README.md
@@ -482,6 +482,7 @@ _If you like this project, please leave me a star._ &#9733;
 |1033|[Moving Stones Until Consecutive](https://leetcode.com/problems/moving-stones-until-consecutive/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1033.java) | |Easy|Math|
 |1030|[Matrix Cells in Distance Order](https://leetcode.com/problems/matrix-cells-in-distance-order/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1030.java) | |Easy|
 |1029|[Two City Scheduling](https://leetcode.com/problems/two-city-scheduling/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1029.java) | |Easy|
+|1026|[Maximum Difference Between Node and Ancestor](https://leetcode.com/problems/maximum-difference-between-node-and-ancestor/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1026.java) | |Medium|Tree, DFS, Binary Tree|
 |1025|[Divisor Game](https://leetcode.com/problems/divisor-game/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1025.java) | |Easy|Math, DP, Brainteaser, Game Theory|
 |1024|[Video Stitching](https://leetcode.com/problems/video-stitching/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1024.java) | |Medium|Array, DP, Greedy|
 |1022|[Sum of Root To Leaf Binary Numbers](https://leetcode.com/problems/sum-of-root-to-leaf-binary-numbers/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1022.java) | |Easy|
diff --git a/src/main/java/com/fishercoder/solutions/_1026.java b/src/main/java/com/fishercoder/solutions/_1026.java
@@ -0,0 +1,44 @@
+package com.fishercoder.solutions;
+
+import com.fishercoder.common.classes.TreeNode;
+
+public class _1026 {
+    public static class Solution1 {
+        /**
+         * My completely original solution on 12/31/2021.
+         */
+        int maxDiff = 0;
+
+        public int maxAncestorDiff(TreeNode root) {
+            dfs(root);
+            return maxDiff;
+        }
+
+        private void dfs(TreeNode root) {
+            if (root == null) {
+                return;
+            }
+            int[] minmax = new int[]{root.val, root.val};
+            findMinMax(root, minmax);
+            maxDiff = Math.max(maxDiff, Math.max(Math.abs(root.val - minmax[0]), Math.abs(minmax[1] - root.val)));
+            dfs(root.left);
+            dfs(root.right);
+        }
+
+        private void findMinMax(TreeNode root, int[] minmax) {
+            if (root == null) {
+                return;
+            }
+            if (root.left != null) {
+                minmax[0] = Math.min(root.left.val, minmax[0]);
+                minmax[1] = Math.max(root.left.val, minmax[1]);
+            }
+            if (root.right != null) {
+                minmax[0] = Math.min(root.right.val, minmax[0]);
+                minmax[1] = Math.max(root.right.val, minmax[1]);
+            }
+            findMinMax(root.left, minmax);
+            findMinMax(root.right, minmax);
+        }
+    }
+}
diff --git a/src/test/java/com/fishercoder/_1026Test.java b/src/test/java/com/fishercoder/_1026Test.java
@@ -0,0 +1,30 @@
+package com.fishercoder;
+
+import com.fishercoder.common.classes.TreeNode;
+import com.fishercoder.common.utils.TreeUtils;
+import com.fishercoder.solutions._1026;
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static org.junit.Assert.assertEquals;
+
+public class _1026Test {
+    private static _1026.Solution1 solution1;
+    private static TreeNode root;
+
+    @Test
+    public void test1() {
+        solution1 = new _1026.Solution1();
+        root = TreeUtils.constructBinaryTree(Arrays.asList(8, 3, 10, 1, 6, null, 14, null, null, 4, 7, 13));
+        assertEquals(7, solution1.maxAncestorDiff(root));
+    }
+
+    @Test
+    public void test2() {
+        solution1 = new _1026.Solution1();
+        root = TreeUtils.constructBinaryTree(Arrays.asList(1, null, 2, null, 0, 3));
+        assertEquals(3, solution1.maxAncestorDiff(root));
+    }
+
+}
