# Binary Tree (Array implementation)

Talking about representation, trees can be represented in two way:
1) Dynamic Node Representation (Linked Representation).
2) Array Representation (Sequential Representation).

We are going to talk about the sequential representation of the trees.
To represent tree using an array, numbering of nodes can start either from 0–(n-1) or 1– n.

```       A(0)
/
B(1)  C(2)
/
D(3)  E(4)   F(6)
OR,
A(1)
/
B(2)  C(3)
/
D(4)  E(5)   F(7)
```

For first case(0—n-1),
if (say)father=p;
then left_son=(2*p)+1;
and right_son=(2*p)+2;

For second case(1—n),
if (say)father=p;
then left_son=(2*p);
and right_son=(2*p)+1;
where father,left_son and right_son are the values of indices of the array.

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Code –

 `// JAVA implementation of tree using array ` `// numbering starting from 0 to n-1. ` `import` `java.util.*; ` `import` `java.lang.*; ` `import` `java.io.*; ` ` `  `class` `Tree { ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``Array_imp obj = ``new` `Array_imp(); ` `        ``obj.Root(``"A"``); ` `    ``//    obj.set_Left("B", 0); ` `        ``obj.set_Right(``"C"``, ``0``); ` `        ``obj.set_Left(``"D"``, ``1``); ` `        ``obj.set_Right(``"E"``, ``1``); ` `        ``obj.set_Left(``"F"``, ``2``); ` `        ``obj.print_Tree(); ` `    ``} ` `} ` ` `  `class` `Array_imp { ` `    ``static` `int` `root = ``0``; ` `    ``static` `String[] str = ``new` `String[``10``]; ` `     `  `    ``/*create root*/` `    ``public` `void` `Root(String key) ` `    ``{ ` `        ``str[``0``] = key; ` `    ``} ` ` `  `    ``/*create left son of root*/` `    ``public` `void` `set_Left(String key, ``int` `root) ` `    ``{ ` `        ``int` `t = (root * ``2``) + ``1``; ` ` `  `        ``if``(str[root] == ``null``){ ` `            ``System.out.printf(````"Can't set child at %d, no parent found "````,t); ` `        ``}``else``{ ` `            ``str[t] = key; ` `        ``} ` `    ``} ` ` `  `    ``/*create right son of root*/` `    ``public` `void` `set_Right(String key, ``int` `root) ` `    ``{ ` `        ``int` `t = (root * ``2``) + ``2``; ` ` `  `        ``if``(str[root] == ``null``){ ` `            ``System.out.printf(````"Can't set child at %d, no parent found "````,t); ` `        ``}``else``{ ` `            ``str[t] = key; ` `        ``} ` `    ``} ` ` `  `    ``public` `void` `print_Tree() ` `    ``{ ` `        ``for` `(``int` `i = ``0``; i < ``10``; i++) { ` `            ``if` `(str[i] != ``null``) ` `                ``System.out.print(str[i]); ` `            ``else` `                ``System.out.print(``"-"``); ` `             `  `        ``} ` `    ``} ` `} `

Output:

```Can't set child at 3, no parent found
Can't set child at 4, no parent found
A-C--F----
```

Note – Please refer this if you want to construct tree from the given parent array.