138 lines
2.8 KiB
Markdown
138 lines
2.8 KiB
Markdown
## 技巧分类：
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- 两指针
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- 滑动窗口
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- 二分法
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- 字符串
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- 数组
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- 哈希表
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- 链表
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- 栈
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- 单调栈
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- 堆
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- 排序
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- 随机
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- 累加和
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- 二进制
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- 贪心算法
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- 树
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- 回溯
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- 图Visited
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- 动态规划
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## python语法
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```python
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# 列表
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range(0, 111, 2) ; range(111, -1, -1)
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for i, num in enumerate(nums):
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nums.index(30) nums.index(30, 2, 5) # 在索引 2 到 5 的范围内查找值 30 的索引
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max_value = max(nums)
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max_index = nums.index(max_value)
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sorted(nums) nums.sort()
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nums.reverse()
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res = [float('inf')] * 6
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[[0] * n for _ in range(m)]
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result.append(path[:])
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```
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```python
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# 栈
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stack = []
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stack.append(s)
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stack.pop()
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```
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```python
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# 字符串
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for c in t: # t is str; c is char
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for c1, c2 in zip(s, t): # s, t are str
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for i, ch in enumerate(s): # s: str
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ord(i) - ord("a")
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chr(66) #将 Unicode 编码值（整数）转换为对应的字符
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str(3)
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int("3")
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s[0:6] # s is str 的切片语法
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repeated_s = s * 3
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s.upper() #不会改变原字符串，如果想要修改，需要重新赋值
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s = "hello" res=list(s) ''.join(res)
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s = s1 + " " + s2
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```
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```python
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# 字典
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count = {}; count[s] = count.get(s, 0) + 1； del count[s]
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count = collections.Counter(s1)
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dic = {}
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count_dict = defaultdict(int) # 使用 int，默认值为 0
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list_dict = defaultdict(list) # 使用 list，默认值为空列表
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set_dict = defaultdict(set) # 使用 set，默认值为空集合
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if s in dic: # s is key
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dic["age"] = 26
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del dic["city"]
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for key in dic:
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for value in dic.values():
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for key, value in dic.items():
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dict(sorted(my_dict.items(), key=lambda item: item[0]))
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```
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```python
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# 队列
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from collections import deque
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d=deque([1, 2, 3, 4, 5])
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d.append(3) d.appendleft(0)
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d.pop() d.popleft()
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d[0] d[-1] # 查看左,右端元素
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```
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```python
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# 堆
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import heapq
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heap = [1, 5, 10]
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heapq.heapify(heap)
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heapq.heappush(heap, 1)
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heapq.heappop(heap)
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heapq.heappush(pri_que, (freq, key)) #小顶堆，大小序按照元组第一个元素freq
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```
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```python
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# 集合
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set = {1, 2, 3, 4}
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set = set([1, 2, 3, 4])
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set = set("aeiouAEIOU")
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set.add(3)
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set.update([1, 5])
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set.remove(2)
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set.pop() 随机删除一个元素
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set1.union(set2)
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if 3 in set:
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```
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```python
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class ListNode:
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def __init__(self, val=0, next=None):
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self.val = val
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self.next = next
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class TreeNode:
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def __init__(self, val=0, left=None, right=None):
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self.val = val
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self.left = left
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self.right = right
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```
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```python
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import bisect
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bisect.bisect_right(nums, x)
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n, r = divmod(n, 10)
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a % b a // b
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lambda x, y: int(x / y)
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from operator import add, sub, mul
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random.randint(1, 6)
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1 << 3 # 将数字 1 左移 3 位 = 8
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# 异或操作符 ^ 的规则是：相同为 0，相异为 1
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x & (x - 1) # 消去x最后一位的1
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x & (~ (x - 1)) # 获得最右边1开始至结尾
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``` |