思路一：可以按层次遍历，每一层从右到左
思路二：使用递归
def mirror_bfs(root):
ret = []
queue = deque([root])
while queue:
node = queue.popleft()
if node:
ret.append(node.val)
queue.append(node.right)
queue.append(node.left)
return ret
def mirror_pre(root):
ret = []
def traversal(root):
if root:
ret.append(root.val)
traversal(root.right)
traversal(root.left)
traversal(root)
return ret每一圈的开始位置总是坐上角元素[0, 0], [1, 1]...
def print_matrix(matrix):
"""
:param matrix: [[]]
"""
rows = len(matrix)
cols = len(matrix[0]) if matrix else 0
start = 0
ret = []
while start * 2 < rows and start * 2 < cols:
print_circle(matrix, start, rows, cols, ret)
start += 1
print ret
def print_circle(matrix, start, rows, cols, ret):
row = rows - start - 1 # 最后一行
col = cols - start - 1
# left->right
for c in range(start, col+1):
ret.append(matrix[start][c])
# top->bottom
if start < row:
for r in range(start+1, row+1):
ret.append(matrix[r][col])
# right->left
if start < row and start < col:
for c in range(start, col)[::-1]:
ret.append(matrix[row][c])
# bottom->top
if start < row and start < col:
for r in range(start+1, row)[::-1]:
ret.append(matrix[r][start])