leetcode的TreeNode工具类
场景
刷题的时候，二叉树类型的题目，用里面的示例数据无法快速构建入参进行测试，顾封装了一个工具类。
代码demo
java
@Slf4j
@Data
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;
}
TreeNode left(int val){
this.left = new TreeNode(val);
return this;
}
TreeNode right(int val){
this.right = new TreeNode(val);
return this;
}
private static final String NULL = "null";
/**
* 构造树
* @param nodes
* @return
*/
public static TreeNode buildTree(Integer[] nodes){
if (nodes.length == 0 || (nodes.length == 1 && Objects.isNull(nodes[0]))){
return null;
}
TreeNode root = new TreeNode(nodes[0]);
Queue<TreeNode> queue = new LinkedList<>();
queue.offer(root);
int pos = 1;
while(!queue.isEmpty() && pos < nodes.length){
TreeNode node = queue.poll();
if (Objects.nonNull(nodes[pos])){
node.left = new TreeNode(nodes[pos]);
queue.offer(node.left);
}
pos++;
if (pos == nodes.length){
break;
}
if (Objects.nonNull(nodes[pos])){
node.right = new TreeNode(nodes[pos]);
queue.offer(node.right);
}
pos++;
}
return root;
}
public static void printTree(TreeNode root){
if (root == null){
log.info("[]");
return;
}
StringBuilder builder = new StringBuilder();
builder.append("[");
Queue<TreeNode> queue = new LinkedList<>();
boolean allEmpty = false;
int size;
queue.offer(root);
while (!queue.isEmpty() && !allEmpty){
allEmpty = true;
size = queue.size();
while (size > 0){
size--;
TreeNode node = queue.poll();
if (node == null){
builder.append(NULL).append(CommonConstants.COMMA);
queue.offer(null);
queue.offer(null);
}
else {
builder.append(node.getVal()).append(CommonConstants.COMMA);
queue.offer(node.left);
queue.offer(node.right);
if (node.left != null || node.right != null){
allEmpty = false;
}
}
}
}
builder.replace(builder.length()-1, builder.length(), "]");
log.info("{}", builder);
}
public static void main(String[] args) {
Integer[] nodes = {4,1,6,0,2,5,7,null,null,null,3,null,null,null,8};
TreeNode root = buildTree(nodes);
}
/**
* 获得最左元素 如果是二叉搜索树即最小元素
* @param root
* @return
*/
public static TreeNode getLeftest(TreeNode root){
if (root == null){
return null;
}
TreeNode item = root, result = item;
while(true){
if (item.left != null){
item = item.left;
result = item;
}
else if (item.right != null){
item = item.right;
}
else {
return result;
}
}
}
/**
* 校验两棵树是否一样
* @param p
* @param q
* @return
*/
public static boolean sameCheck(TreeNode p, TreeNode q){
if (Objects.isNull(p) && Objects.isNull(q)){
return true;
}
if (Objects.isNull(p) || Objects.isNull(q) || p.getVal() != q.getVal()){
return false;
}
return sameCheck(p.getLeft(), q.getLeft()) && sameCheck(p.getRight(), q.getRight());
}
/**
* 根据字符串值构造数据
* @param s
* @return
*/
public static TreeNode constructNode(String s){
if (NULL.equals(s)){
return null;
}
return new TreeNode(Integer.parseInt(s));
}
}