[Leetcode brush question] Algorithm: the sum of two numbers

1. Topic description

Two, try 1

from typing import List
class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        num_dict = {
    
    }

        for i in range(len(nums)):
            diff = target - nums[i]

            if diff in num_dict:
                return [num_dict[diff], i]

            num_dict[nums[i]] = i

        return []

Three, try 2

from typing import List

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        num_dict = {
    
    }

        for i, num in enumerate(nums):
            diff = target - num
            
            if diff in num_dict:
                return [num_dict[diff], i]
            
            num_dict[num] = i
        
        return []

Fourth, try 3

from typing import List

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        nums_sorted = sorted(enumerate(nums), key=lambda x: x[1])
        left, right = 0, len(nums) - 1

        while left < right:
            curr_sum = nums_sorted[left][1] + nums_sorted[right][1]

            if curr_sum == target:
                return [nums_sorted[left][0], nums_sorted[right][0]]

            if curr_sum < target:
                left += 1
            else:
                right -= 1

        return []

Five, try 4

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        records = dict()

        # 用枚举更方便，就不需要通过索引再去取当前位置的值
        for idx, val in enumerate(nums):
            if target - val not in records:
                records[val] = idx
            else:
                return [records[target - val], idx]