226. Invert Binary Tree

本文介绍了一种简单有效的翻转二叉树算法,通过递归地交换节点的左右子树来实现整个二叉树的翻转。文章提供了一个具体的翻转二叉树的示例及其对应的Java代码实现。

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Invert a binary tree.

     4
   /   \
  2     7
 / \   / \
1   3 6   9
to
     4
   /   \
  7     2
 / \   / \
9   6 3   1
Trivia:

This problem was inspired by this original tweet by Max Howell:



思路很简单,【递归地】交换节点的左右子树。


 public TreeNode invertTree(TreeNode root)
	{
		if(root!=null)
			change(root);
		return root;
	}
	
	public void change(TreeNode t)
	{
		if(t.left!=null)
			change(t.left);
		
		if(t.right!=null)
			change(t.right);
		
		TreeNode temp=t.right;
		t.right=t.left;
		t.left=temp;
	}


import cv2 import numpy as np def is_approx_rect(contour, epsilon_factor=0.02): peri = cv2.arcLength(contour, True) approx = cv2.approxPolyDP(contour, epsilon_factor * peri, True) return (4 <= len(approx) <= 5 and cv2.isContourConvex(approx)), approx def calc_center(approx): M = cv2.moments(approx) if M["m00"] == 0: return None return int(M["m10"] / M["m00"]), int(M["m01"] / M["m00"]) def distance(p1, p2): return np.sqrt((p1[0]-p2[0])**2 + (p1[1]-p2[1])**2) def main(): cap = cv2.VideoCapture("222.mp4") if not cap.isOpened(): print("打开视频失败") return prev_center = None while True: ret, frame = cap.read() if not ret: break gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) _, binary = cv2.threshold(gray, 120, 255, cv2.THRESH_BINARY_INV) closed = cv2.morphologyEx(binary, cv2.MORPH_CLOSE, cv2.getStructuringElement(cv2.MORPH_RECT, (50, 50))) contours_data = cv2.findContours(closed, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE) contours = contours_data[1] if len(contours_data) == 3 else contours_data[0] candidates = [] for cnt in contours: is_rect, approx = is_approx_rect(cnt) if is_rect: center = calc_center(approx) if center: candidates.append((approx, center, cv2.contourArea(approx))) if not candidates: selected = None elif prev_center is None: selected = max(candidates, key=lambda x: x[2]) else: candidates.sort(key=lambda x: distance(x[1], prev_center)) top_n = [candidates[0]] for c in candidates[1:]: if distance(c[1], prev_center) - distance(candidates[0][1], prev_center) < 50: top_n.append(c) else: break selected = max(top_n, key=lambda x: x[2]) display_frame 将上述代码改成适用于 openmv4 h7 plus 的代码要求给出完整代码
08-03
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