ZhouYang1993

cities = {'London': 'UK', 'Tokyo': 'Japan', 'New York': 'US'}
# Method 1
reversed_cities = {v: k for k, v in cities.items()}
print(reversed_cities)
# {'UK': 'London', 'Japan': 'Tokyo', 'US': 'New York'}

# Method 2
reversed_cities = dict(zip(cities.values(), cities.keys()))
print(reversed_cities)

ZhouYang1993

transpose_mat =lambda A:[list(i) for i in zip(*A)]

ZhouYang1993

add_vec= lambda A,B:[ai+bi for (ai, bi) in zip(A, B)]

ZhouYang1993

dist = lambda w,v : (sum((wi - vi)**2 for wi,vi in zip(w,v)))**.5

ZhouYang1993

fib = lambda x: x if x <= 1 else fib(x - 1) + fib(x - 2)

ZhouYang1993

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
from collections import deque
class Solution:
    def maxDepth(self, root: Optional[TreeNode]) -> int:
        depth = 0

ZhouYang1993

from collections import deque


class Solution:
    def isValid(self, s: str) -> bool:
        mapping = {')': '(', ']': '[', '}': '{'}
        stack = deque()
        for char in s:
            if mapping.get(char):
                if len(stack) == 0:

ZhouYang1993

from collections import deque

dq1=deque('abcde')
print(dq1)
# deque(['a', 'b', 'c', 'd', 'e'])

# Insert an item in the middle
dq1.insert(2,'f')
print(dq1)
# deque(['a', 'b', 'f', 'c', 'd', 'e'])

ZhouYang1993

from collections import deque

dq1=deque([1,2,3,4,5])
print(dq1)
# deque([1, 2, 3, 4, 5])
dq1.popleft()
print(dq1)
# deque([2, 3, 4, 5])
dq1.appendleft(9)
print(dq1)

ZhouYang1993

from collections import deque

dq1=deque([1,2,3,4,5])
print(dq1)
# deque([1, 2, 3, 4, 5])
dq2=deque('abcde')
print(dq2)
# deque(['a', 'b', 'c', 'd', 'e'])
dq3=deque([i for i in range(10) if i%2==0])
print(dq3)