• # Java数组实现顺序存储二叉树，进行前中后序遍历

``````/** 用数组实现顺序存储完全二叉树，并进行前序遍历中序遍历后序遍历
*         1
*       /
*      2    3
*     /   /
*    4  5 6
*/
public class ArrayBinaryTreeDemo {
public static void main(String[] args) {
int[] tree = {1, 2, 3, 4, 5, 6};
ArrayBinaryTree arrayBinaryTree = new ArrayBinaryTree(tree);
arrayBinaryTree.preOrder();   // 1 2 4 5 3 6
arrayBinaryTree.infixOrder(); // 4 2 5 1 6 3
arrayBinaryTree.postOrder();  // 4 5 2 6 3 1
}
}

class ArrayBinaryTree {
private int[] arr;

public ArrayBinaryTree(int[] arr) {
this.arr = arr;
}

/**
* 先序遍历
*/
public void preOrder() {
if (arr == null || arr.length == 0) {
System.out.println("树为空！");
return;
}
preOrder(0);
System.out.println();
}

/**
* 中序遍历
*/
public void infixOrder() {
if (arr == null || arr.length == 0) {
System.out.println("树为空！");
return;
}
infixOrder(0);
System.out.println();
}

/**
* 后序遍历
*/
public void postOrder() {
if (arr == null || arr.length == 0) {
System.out.println("树为空！");
return;
}
postOrder(0);
System.out.println();
}

private void infixOrder(int index) {
int left = index * 2 + 1; // 左子节点index
if (left < arr.length) infixOrder(left);
System.out.print(arr[index] + " ");
int right = index * 2 + 2; // 右子节点index
if (right < arr.length) infixOrder(right);
}

private void postOrder(int index) {
int left = index * 2 + 1;
if (left < arr.length) postOrder(left);
int right = index * 2 + 2;
if (right < arr.length) postOrder(right);
System.out.print(arr[index] + " ");
}

private void preOrder(int index) {
System.out.print(arr[index] + " ");
int left = index * 2 + 1;
if (left < arr.length) {
preOrder(left);
}
int right = index * 2 + 2;
if (right < arr.length) {
preOrder(right);
}
}
}``````
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