Create trees2.java

trees2.java

@@ -0,0 +1,70 @@
+//problem1
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    public TreeNode buildTree(int[] inorder, int[] postorder) {
+        if(inorder.length==0) return null;
+        int rootval=postorder[postorder.length-1];
+        int idx=-1;
+        for(int i=0;i<inorder.length;i++){
+            if(inorder[i]==rootval){
+                idx=i;
+                break;
+            }
+        }
+        TreeNode root=new TreeNode(rootval);
+        int[] inleft=Arrays.copyOfRange(inorder,0,idx);
+        int[] inright=Arrays.copyOfRange(inorder,idx+1,inorder.length);
+        int[] postleft=Arrays.copyOfRange(postorder,0,inleft.length);
+        int[] postright=Arrays.copyOfRange(postorder,inleft.length,postorder.length-1);
+        root.left=buildTree(inleft,postleft);
+        root.right=buildTree(inright,postright);
+        return root;
+    }
+}
+//problem2
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    public int sumNumbers(TreeNode root) {
+        String ans="";
+        if(root==null) return 0;
+        return totalsum(root,ans);
+    }
+    private int totalsum(TreeNode root,String ans){
+        int sum=0;
+        if(root==null) return 0;
+        ans+=root.val;
+        if(root.left==null && root.right==null){
+            return Integer.parseInt(ans);
+        }
+        return totalsum(root.left,ans)+totalsum(root.right,ans);
+
+    }
+}