Simulation
Number & Calculation
- 数字：
- 长度变化：进位， 借1
- 运算：
- 优先级
- 从左到右
def evaluate(operator, x, y = 0):
if operator == "+":
return x
if operator == "-":
return -x
if operator == "*":
return x * y
return int(float(x) / y)
# Python2: (-3/2) --> floor(-1.5) --> -2
# Python3: (-3/2) --> (-1.5) --> int(-1.5) = -1
stack = []
curr = 0
previous_op = "+"
s += "@"
for ch in s:
if ch.isdigit():
curr = curr * 10 + int(ch)
elif ch == "(":
stack.append(previous_op)
previous_op = "+"
else:
if previous_op in "*/":
stack.append(evaluate(previous_op, stack.pop(), curr))
else:
stack.append(evaluate(previous_op, curr, 0))
curr = 0
previous_op = ch
if ch == ")":
while type(stack[-1]) == int:
curr += stack.pop()
previous_op = stack.pop()
return sum(stack)
What I have done
227. Basic Calculator II
772. Basic Calculator III
738. Monotone Increasing Digits
Else
What I have done
54. Spiral Matrix
59. Spiral Matrix II
735. Asteroid Collisionwhile loop看清楚边界条件，容易数组越界
Random
Template
random.randrange(start, stop[, step])
random.randint(1, stop)
random.uniform(0, 1) # 生成一个在 [0, 1) 区间的均匀随机浮点数。
math.sqrt(random.uniform(0, 1)) # 对生成的随机数求平方根，目的是为了在圆内生成点时保证每个位置的概率分布是均匀的
# 若直接使用随机数的比例，会导致生成的点集中在圆心附近，因为面积密度和半径成平方关系。平方根修正可以平衡分布
What I have done
497.Random Point in Non-overlapping Rectangles
Read Data / OOD / Data Structure
What I have done
355. Design Twitter
1268. Search Suggestions System
1347. Minimum Number of Steps to Make Two Strings Anagram
1472. Design Browser History