From 23bf92a1e92e6870d410f3b9ab25b8ca99bf3d89 Mon Sep 17 00:00:00 2001
From: 3wish <hety13@chinaunicom.cn>
Date: Mon, 4 Dec 2023 12:48:44 +0800
Subject: [PATCH] =?UTF-8?q?=E9=80=92=E5=BD=92=E5=92=8C=E5=8A=A8=E6=80=81?=
=?UTF-8?q?=E8=A7=84=E5=88=92?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
---
.gitignore | 4 +-
dynamic_programming/dynamic_programming.py | 52 ++++++++++++++++++
interview/iter_tree.py | 27 ++++++++++
link_list/singly_link.py | 49 +++++++++++++++++
recursive/recursive.py | 61 ++++++++++++++++++++++
test/test_dynamic_programming.py | 12 +++++
test/test_link_list.py | 12 +++++
test/test_recursive.py | 10 ++++
8 files changed, 226 insertions(+), 1 deletion(-)
create mode 100644 dynamic_programming/dynamic_programming.py
create mode 100644 interview/iter_tree.py
create mode 100644 link_list/singly_link.py
create mode 100644 recursive/recursive.py
create mode 100644 test/test_dynamic_programming.py
create mode 100644 test/test_link_list.py
create mode 100644 test/test_recursive.py
diff --git a/.gitignore b/.gitignore
index cdd4b45..bf0191b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,4 @@
.venv
-test/.pytest_cache/
\ No newline at end of file
+.idea
+test/.pytest_cache/
+**/__pycache__
\ No newline at end of file
diff --git a/dynamic_programming/dynamic_programming.py b/dynamic_programming/dynamic_programming.py
new file mode 100644
index 0000000..796557f
--- /dev/null
+++ b/dynamic_programming/dynamic_programming.py
@@ -0,0 +1,52 @@
+"""
+动态规划的核心：
+将大问题分解为多个小问题，通过解决一个个小问题，
+并保存解决每个小问题时的状态最终解决大问题
+
+动态规划实现找零：
+1. 先看找零1元需要多少：1
+2. 找零2元需要多少：两张1元
+3. 找零3元需要多少：找零2元的结果+找零1元的结果
+"""
+
+
+# 动态规划找零
+def dp_rec_mc1(changes: list[int], cash: int):
+ min_changes = [0 for _ in range(cash + 1)]
+ for i in range(1, cash + 1):
+ min_amount = i
+ for c in filter(lambda x: x <= i, changes):
+ temp_min_amount = 1 + min_changes[i - c]
+ if temp_min_amount < min_amount:
+ min_amount = temp_min_amount
+
+ min_changes[i] = min_amount
+
+ return min_changes[cash]
+
+
+# 动态规划找零，并保存每一种找零所需的纸币情况
+def dp_rec_mc2(changes: list[int], cash: int):
+ change_used: dict[int, dict[int, int]] = {}
+ min_amounts = [0 for _ in range(cash + 1)]
+ for i in range(1, cash + 1):
+ min_amount = i
+ changes_less_then_i = filter(lambda x: x <= i, changes)
+ for c in changes_less_then_i:
+ temp_min_amount = 1 + min_amounts[i - c]
+ if temp_min_amount < min_amount:
+ min_amount = temp_min_amount
+ if i - c > 0:
+ change_used[i] = change_used[i - c].copy()
+ if change_used[i].get(c):
+ change_used[i][c] += 1
+ else:
+ change_used[i][c] = 1
+ else:
+ change_used[i] = {c: 1}
+
+ min_amounts[i] = min_amount
+ if min_amount == i:
+ change_used[i] = {1: i}
+ return change_used[cash]
+
diff --git a/interview/iter_tree.py b/interview/iter_tree.py
new file mode 100644
index 0000000..9c73db3
--- /dev/null
+++ b/interview/iter_tree.py
@@ -0,0 +1,27 @@
+class Node:
+ def __init__(self, value: int, children=None):
+ self.value = value
+ self.children = children
+
+
+nodes1 = Node(1, [Node(2, [Node(4), Node(5)]), Node(3, [Node(6), Node(7)])])
+
+nodes2 = Node(1, [Node(2, [Node(4), Node(5), Node(10, [Node(19), Node(39), Node(27)])]), Node(3, [Node(6), Node(7)])])
+
+
+def iter_tree(node: Node):
+ res = [node.value]
+
+ def recursive(nodes: list[Node], temp_res: list[int]):
+ temp = []
+ for _node in nodes:
+ temp_res.append(_node.value)
+ if _node.children:
+ temp.extend(_node.children)
+ if len(temp) > 0:
+ recursive(temp, temp_res)
+
+ if node.children:
+ recursive(node.children, res)
+
+ return res
diff --git a/link_list/singly_link.py b/link_list/singly_link.py
new file mode 100644
index 0000000..1a8688d
--- /dev/null
+++ b/link_list/singly_link.py
@@ -0,0 +1,49 @@
+from typing import Self
+
+
+class SinglyNode:
+ def __init__(self, value, nex: Self | None):
+ self.value = value
+ self.next = nex
+
+ def __repr__(self):
+ return f'Node({self.value})'
+
+class SinglyLinkList:
+
+ __string = ''
+
+ def __init__(self):
+ self.size = 0
+ self.head: SinglyNode | None = None
+
+ def __repr__(self):
+ return self.__string
+
+ def is_empty(self) -> bool:
+ return self.size == 0
+
+ # 新节点总是添加到头部
+ def push(self, value):
+ if self.head is None:
+ self.__string = f'{value} -> None'
+ else:
+ self.__string = f'{value} -> ' + self.__string
+ node = SinglyNode(value, self.head)
+ self.head = node
+ self.size += 1
+
+ def pop(self) -> SinglyNode:
+ head = self.head
+ node = self.head.next
+ self.head = node
+ return head
+
+ def peek(self):
+ return self.head.value
+
+ def iter(self):
+ cur = self.head
+ while cur:
+ yield cur.value
+ cur = cur.next
diff --git a/recursive/recursive.py b/recursive/recursive.py
new file mode 100644
index 0000000..d544a18
--- /dev/null
+++ b/recursive/recursive.py
@@ -0,0 +1,61 @@
+"""
+递归三定律：
+1 递 归 算 法 必 须 具 有 基 本 情 况
+2 递 归 算 法 必 须 向 基 本 情 况 靠 近
+3 递 归 算 法 必 须 以 递 归 方 式 调 用 自 身
+"""
+
+def recursive_sum(nums: list):
+ if 1 == len(nums):
+ return nums[0]
+
+ return nums[0] + recursive_sum(nums[1:])
+
+
+# 使用递归的方式实现进制转换
+def recursive_num_conversion(num: int) -> str:
+ if num == 0:
+ return ''
+
+ return recursive_num_conversion(num // 2) + str(num % 2)
+
+
+# 找零问题：类似贪婪，经量找出最少纸币搭配
+def rec_mc1(changes: list[int], cash: int):
+ # 全用1元纸币时最少找零数
+ min_amount = cash
+
+ try:
+ if changes.index(cash):
+ return 1
+ except Exception as e:
+ for c in changes:
+ # cash - c，表示使用了一张面额为c的来找零，所以需要+1
+ num = 1 + rec_mc1(changes, cash-c)
+
+ if num < min_amount:
+ min_amount = num
+
+ return min_amount
+
+
+def rec_mc2(changes: list[int], cash: int, min_changes: int,):
+ min_amount = cash
+
+ try:
+ if changes.index(cash):
+ min_changes[cash] = 1
+ return 1
+ except Exception as e:
+ if min_changes[cash] > 0:
+ return min_changes[cash]
+ else:
+ for c in changes:
+ num = 1 + rec_mc2(changes, cash - c, min_changes)
+
+ if num < min_amount:
+ min_amount = num
+ min_changes[cash] = min_amount
+
+ return min_amount
+
diff --git a/test/test_dynamic_programming.py b/test/test_dynamic_programming.py
new file mode 100644
index 0000000..70bed37
--- /dev/null
+++ b/test/test_dynamic_programming.py
@@ -0,0 +1,12 @@
+from dynamic_programming.dynamic_programming import *
+
+
+def test_dp_rec_mc1():
+ cash = 49
+ changes = [1, 5, 10, 20, 50]
+ assert 7 == dp_rec_mc1(changes, cash)
+
+
+def test_dp_rec_mc2():
+ cash = 49
+ changes = [1, 5, 10, 20, 50]
\ No newline at end of file
diff --git a/test/test_link_list.py b/test/test_link_list.py
new file mode 100644
index 0000000..adde84d
--- /dev/null
+++ b/test/test_link_list.py
@@ -0,0 +1,12 @@
+from link_list.singly_link import SinglyLinkList
+
+def test_singly_link():
+ link_list = SinglyLinkList()
+ link_list.push(1)
+ link_list.push(2)
+ link_list.push(3)
+ link_list.push(4)
+
+ assert 4 == link_list.peek()
+ assert 4 == link_list.size
+ assert "4 -> 3 -> 2 -> 1 -> None" == repr(link_list)
\ No newline at end of file
diff --git a/test/test_recursive.py b/test/test_recursive.py
new file mode 100644
index 0000000..201f431
--- /dev/null
+++ b/test/test_recursive.py
@@ -0,0 +1,10 @@
+from recursive.recursive import *
+
+
+def test_recursive_sum():
+ nums = [1, 2, 3]
+ assert 6 == recursive_sum(nums)
+
+def test_recursive_num_conversion():
+ num = 10
+ assert '1010' == recursive_num_conversion(num)
\ No newline at end of file