Algorithms/InvertTree.java at master · abiaps/Algorithms · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
/* Inverting the tree is just swapping the children */

public class InvertTree {
	            public static TreeNode invertTree(TreeNode root)
	            {
	                  if(root==null)
                  	  return null;
		          if(root!=null)
		          invert(root);
		          return root;
		     }
		     public static TreeNode invert(TreeNode dup_root)
		     {
			 if(dup_root.left==null&&dup_root.right!=null) // when one of the children is null
			 {
			        TreeNode temp=dup_root.left;                //swapping occurs
				dup_root.left=dup_root.right;
				dup_root.right=temp;
				if(dup_root.left!=null)
				invert(dup_root.left);                      //recursive calls on going down the tree
				if(dup_root.right!=null)
				invert(dup_root.right);
			 }
			 else if(dup_root.right==null&&dup_root.left!=null)
			 {
			        TreeNode temp=dup_root.left;
				dup_root.left=dup_root.right;
				dup_root.right=temp;
				if(dup_root.right!=null)
				invert(dup_root.right);
				if(dup_root.left!=null)
				invert(dup_root.left);
			 }
			 if(dup_root.left!=null&&dup_root.right!=null)  // when both the children are not null
			 {
			        TreeNode temp=dup_root.left;
			        dup_root.left=dup_root.right;
			        dup_root.right=temp;
			        invertTree(dup_root.left);
			        invertTree(dup_root.right);
			 }
			        return dup_root;
		}

	public static void main(String[] args) {

      	TreeNode root=new TreeNode(4);
      	TreeNode l1=new TreeNode(2);
 	root.left=l1;
      	TreeNode r1=new TreeNode(7);
      	root.right=r1;
      	TreeNode l2=new TreeNode(1);
      	l1.left=l2;
      	TreeNode r2=new TreeNode(3);
      	l1.right=r2;
      	TreeNode l3=new TreeNode(6);
      	r1.left=l3;
      	TreeNode r3=new TreeNode(9);
      	r1.right=r3;
      	invertTree(root);
	}

}