leetcode 1-10（2024.08.14）

立个flag，1-100题每天分配10题，不会就先空着（4，5，8，10）。

1. 1：两数之和

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        haxi = {}
        for i, num in enumerate(nums):
            if target - num in haxi:
                return [haxi[target - num], i]
            else:
                haxi[num] = i

2. 2：两数相加

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
        dummy = res = ListNode()
        add = 0
        while l1 or l2:
            val1 = l1.val if l1 else 0
            val2 = l2.val if l2 else 0
            val = add + val1 + val2
            res.next = ListNode(val % 10)
            add = val // 10
            l1 = l1.next if l1 else None
            l2 = l2.next if l2 else None
            res = res.next
        if add:
            res.next = ListNode(add)
        return dummy.next

3. 3：无重复字符的最长子串

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        left = 0
        right = 0
        res = 0
        haxi = {}
        for i in range(len(s)):
            if s[i] in haxi and haxi[s[i]] >= left:
                leng = right - left
                res = leng if leng > res else res
                left = haxi[s[i]] + 1
            haxi[s[i]] = i
            right = right + 1
        leng = right - left
        res = leng if leng > res else res
        return res

4. 4：寻找两个正序数组的中位数

5. 5：最长回文子串

6. 6：Z字形变换

class Solution:
    def convert(self, s: str, numRows: int) -> str:
        if numRows == 1:  # 行数为1，直接返回原字符串
            return s
        matrix = []
        for i in range(numRows):
            matrix.append("")
        period = numRows + numRows - 2
        idx = 0
        num = 0
        for st in s:
            matrix[idx] = matrix[idx] + st
            num = num + 1
            if 0 < num % period < numRows:
                idx = idx + 1
            else:
                idx = idx - 1
        res = ""
        for i in matrix:
            res = res + i
        return res

7. 7：整数反转

class Solution:
    def reverse(self, x: int) -> int:
        def get_length(x):
            leng = 0
            while x:
                x = x // 10
                leng = leng + 1
            return leng
        def get_reverse(x, leng):
            res = 0
            while x:
                num = x % 10
                res = res + num * 10 ** (leng - 1)
                leng = leng - 1
                x = x // 10
            return res
 
        if x > 0:
            leng = get_length(x)
            res = get_reverse(x, leng)
        elif x == 0:
            res = 0
        elif x < 0:
            leng = get_length(-x)
            res = - get_reverse(-x, leng)
        return res if -2 ** 31 <= res <= 2 ** 31 - 1 else 0

8. 8. 字符串转换整数 

9. 9：回文数

class Solution:
    def isPalindrome(self, x: int) -> bool:
        def get_length(x):
            leng = 0
            while x:
                x = x // 10
                leng = leng + 1
            return leng
        def get_reverse(x, leng):
            res = 0
            while x:
                num = x % 10
                res = res + num * 10 ** (leng - 1)
                leng = leng - 1
                x = x // 10
            return res
 
        if x > 0:
            leng = get_length(x)
            res = get_reverse(x, leng)
            return res == x
        elif x == 0:
            return True
        elif x < 0:
            return False

10. 10：正则表达式匹配