feat: add leetcode75 day31

add leetcode75 day31

Author: hj.tian

leetcode75/day31_155.py

@@ -0,0 +1,46 @@
+from typing import List, Tuple
+
+
+class MinStack:
+ """
+ stack
+ (-3, -3)
+ (0, -2)
+ (-2, -2)
+ """
+
+ def __init__(self):
+ self.stack: List[Tuple[int, int]] = []
+
+ def push(self, val: int) -> None:
+ if len(self.stack) == 0:
+ self.stack.append((val, val))
+ else:
+ cur_mins = self.stack[-1][1]
+ if val < cur_mins:
+ self.stack.append((val, val))
+ else:
+ self.stack.append((val, cur_mins))
+
+ def pop(self) -> None:
+ self.stack = self.stack[:-1]
+
+ def top(self) -> int:
+ if self.stack:
+ return self.stack[-1][0]
+
+ def getMin(self) -> int:
+ if self.stack:
+ return self.stack[-1][1]
+
+
+if __name__ == "__main__":
+ # Your MinStack object will be instantiated and called as such:
+ obj = MinStack()
+ obj.push(-2)
+ obj.push(0)
+ obj.push(-3)
+ assert obj.getMin() == -3
+ obj.pop()
+ assert obj.top() == 0
+ assert obj.getMin() == -2

leetcode75/day31_208.py

@@ -0,0 +1,59 @@
+class Trie:
+ """
+ root {}
+
+ a {a: {}}
+
+ p {a: {p: {}}}
+
+ p {a: {p: {p: {}}}}
+
+ l {a: {p: {p: {l: {}}}}}
+
+ e {a: {p: {p: {l: {e: {}}}}}}
+
+ $ {a: {p: {p: {l: {e: {$:$}}}}}}
+
+ after insert app
+ {a: {p: {p: {
+ l: {e: {$:$}},
+ $: $
+ }}}}
+ """
+
+ def __init__(self):
+ self.root = {}
+
+ def insert(self, word: str) -> None:
+ root = self.root
+ for char in word:
+ if char not in root:
+ root[char] = {}
+ root = root[char]
+ root["$"] = "$"
+
+ def search(self, word: str) -> bool:
+ root = self.root
+ for char in word:
+ if char not in root:
+ return False
+ root = root[char]
+ return root.get("$") == "$"
+
+ def startsWith(self, prefix: str) -> bool:
+ root = self.root
+ for char in prefix:
+ if char not in root:
+ return False
+ root = root[char]
+ return True
+
+
+if __name__ == "__main__":
+ trie = Trie()
+ trie.insert("apple")
+ assert trie.search("apple") is True
+ assert trie.search("app") is False
+ assert trie.startsWith("app") is True
+ trie.insert("app")
+ assert trie.search("app") is True

leetcode75/day31_232.py

@@ -0,0 +1,56 @@
+class MyQueue:
+ """
+ stack: 后入先出
+ queue: 先入先出
+
+ stack1 stack2
+
+ | | | |
+ | 2 | | |
+ | 1 | | |
+
+ push 操作: 往 stack1 里压
+ peek 操作:
+ 1. stack2 空: stack1 所有出栈并依次压入 stack2, 返回 stack2 栈顶
+ 2. stack2 非空: 直接返回 stack2 栈顶
+ pop 操作:
+ 1. stack2 空: stack1 所有出栈并依次压入 stack2, 弹出 stack2 栈顶
+ 2. stack2 非空: 直接弹出 stack2 栈顶
+ empty:
+ stack2 is empty and stack1 is empty
+ """
+
+ def __init__(self):
+ self.stack1 = []
+ self.stack2 = []
+
+ def push(self, x: int) -> None:
+ self.stack1.append(x)
+
+ def pop(self) -> int:
+ ans = self.peek()
+ self.stack2 = self.stack2[:-1]
+ return ans
+
+ def peek(self) -> int:
+ if len(self.stack2) == 0:
+ self.stack2 = self.stack1[::-1]
+ self.stack1 = []
+ if len(self.stack2) > 0:
+ return self.stack2[-1]
+
+ def empty(self) -> bool:
+ return len(self.stack1) == len(self.stack2) == 0
+
+
+if __name__ == "__main__":
+ # Your MyQueue object will be instantiated and called as such:
+ obj = MyQueue()
+ obj.push(1)
+ obj.push(2)
+ assert obj.peek() == 1
+ assert obj.pop() == 1
+ assert obj.empty() is False
+ assert obj.pop() == 2
+ assert obj.pop() is None
+ assert obj.empty() is True