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TreeNode.java
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75 lines (65 loc) · 2.02 KB
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package normal;
/**
* @program JavaBooks
* @description: 二叉树
* @author: mf
* @create: 2019/09/06 10:05
*/
public class TreeNode {
int val;
TreeNode left;
TreeNode right;
public TreeNode(int val) {
this.val = val;
}
// 给定一个前序和中序数组，生成一颗二叉树 // 根据T7笔试题
public static TreeNode setBinaryTree(int[] pre, int[] in) {
TreeNode root = reConstructBinaryTree(pre, 0, pre.length - 1, in, 0, in.length - 1);
return root;
}
private static TreeNode reConstructBinaryTree(int[] pre, int startPre, int endPre, int[] in, int startIn, int endIn) {
if (startPre > endPre || startIn > endIn) {
return null;
}
TreeNode root = new TreeNode(pre[startPre]);
for (int i = startIn; i <= endIn; i++) {
if (in[i] == pre[startPre]) {
root.left = reConstructBinaryTree(pre, startPre + 1, startPre + i - startIn, in, startIn, i - 1);
root.right = reConstructBinaryTree(pre, i - startIn + startPre + 1, endPre, in, i + 1, endIn);
}
}
return root;
}
// 递归打印前序
public static void preOrderRe(TreeNode root) {
System.out.println(root.val);
TreeNode leftNode = root.left;
if (leftNode != null) {
preOrderRe(leftNode);
}
TreeNode rightNode = root.right;
if (rightNode != null) {
preOrderRe(rightNode);
}
}
// 递归打印中序
public static void midOrderRe(TreeNode node) {
if (node == null) {
return;
} else {
midOrderRe(node.left);
System.out.println(node.val);
midOrderRe(node.right);
}
}
// 递归打印后序
public static void postOrderRe(TreeNode node) {
if (node == null) {
return;
} else {
postOrderRe(node.left);
postOrderRe(node.right);
System.out.println(node.val);
}
}
}