617. Merge Two Binary Trees

Author: zhaoguanchen

README.md

@@ -83,6 +83,7 @@ The project is divided into two parts: `structure` and `solution`.
 | 515  | [Find Largest Value in Each Tree Row](https://leetcode.com/problems/find-largest-value-in-each-tree-row/) | Medium     | [FindLargestValueInEachTreeRow.java](src/leetcode/solution/tree/FindLargestValueInEachTreeRow.java) | BFS \|DFS                                                    |
 | 404  | [Sum of Left Leaves](https://leetcode.com/problems/sum-of-left-leaves/) | Easy       | [SumOfLeftLeaves.java](src/leetcode/solution/tree/SumOfLeftLeaves.java) | DFS                                                          |
 | 513  | [Find Bottom Left Tree Value](https://leetcode.com/problems/find-bottom-left-tree-value/) | Medium     | [FindBottomLeftTreeValue.java](src/leetcode/solution/tree/FindBottomLeftTreeValue.java) | DFS                                                          |
+| 617  | [Merge Two Binary Trees](https://leetcode.com/problems/merge-two-binary-trees/) | Easy       | [MergeTwoBinaryTrees.java](src/leetcode/solution/tree/MergeTwoBinaryTrees.java) | DFS                                                          |
 | 662  | [Maximum Width of Binary Tree](https://leetcode.com/problems/maximum-width-of-binary-tree/) | Medium     | [MaximumWidthOfBinaryTree.java](src/leetcode/solution/tree/MaximumWidthOfBinaryTree.java) | BFS \|DFS + The relationship of the index between the father node and the child node. |
 | 979  | [Distribute Coins in Binary Tree](https://leetcode.com/problems/distribute-coins-in-binary-tree/) | Medium     | [DistributeCoinsInBinaryTree.java](src/leetcode/solution/tree/DistributeCoinsInBinaryTree.java) | DFS                                                          |
 | 1302 | [Deepest Leaves Sum](https://leetcode.com/problems/deepest-leaves-sum/) | Medium     | [DeepestLeavesSum.java](src/leetcode/solution/tree/DeepestLeavesSum.java) | BFS \| DFS                                                   |

src/leetcode/solution/tree/MergeTwoBinaryTrees.java

@@ -0,0 +1,42 @@
+package leetcode.solution.tree;
+
+import leetcode.structure.TreeNode;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 617. Merge Two Binary Trees
+ */
+public class MergeTwoBinaryTrees {
+
+    public static void main(String[] args) {
+        Integer[] array1 = {1, 2, 3, null, 5, null, 4};
+        TreeNode r1 = TreeNode.constructTree(array1);
+        Integer[] array2 = {1, 2, 3, null, 5, null, 4};
+        TreeNode r2 = TreeNode.constructTree(array2);
+
+        MergeTwoBinaryTrees view = new MergeTwoBinaryTrees();
+        TreeNode ans = view.mergeTrees(r1, r2);
+        System.out.println(TreeNode.print(ans));
+    }
+
+    public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
+        if (root1 == null) {
+            return root2;
+        }
+
+        if (root2 == null) {
+            return root1;
+        }
+
+        root1.val += root2.val;
+
+        root1.left = mergeTrees(root1.left, root2.left);
+        root1.right = mergeTrees(root1.right, root2.right);
+
+
+        return root1;
+    }
+
+}