Update 0001.两数之和.md

problems/0001.两数之和.md

@@ -151,7 +151,7 @@ public int[] twoSum(int[] nums, int target) {
 ```
 
 Python：
-
+（版本一） 使用字典
 ```python
 class Solution:
     def twoSum(self, nums: List[int], target: int) -> List[int]:
@@ -163,6 +163,53 @@ class Solution:
             records[value] = index    # 遍历当前元素，并在map中寻找是否有匹配的key
         return []
 ```
+（版本二）使用集合
+```python
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        #创建一个集合来存储我们目前看到的数字
+        seen = set()             
+        for i, num in enumerate(nums):
+            complement = target - num
+            if complement in seen:
+                return [nums.index(complement), i]
+            seen.add(num)
+```
+（版本三）使用双指针
+```python
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        # 对输入列表进行排序
+        nums_sorted = sorted(nums)
+        
+        # 使用双指针
+        left = 0
+        right = len(nums_sorted) - 1
+        while left < right:
+            current_sum = nums_sorted[left] + nums_sorted[right]
+            if current_sum == target:
+                # 如果和等于目标数，则返回两个数的下标
+                left_index = nums.index(nums_sorted[left])
+                right_index = nums.index(nums_sorted[right])
+                if left_index == right_index:
+                    right_index = nums[left_index+1:].index(nums_sorted[right]) + left_index + 1
+                return [left_index, right_index]
+            elif current_sum < target:
+                # 如果总和小于目标，则将左侧指针向右移动
+                left += 1
+            else:
+                # 如果总和大于目标值，则将右指针向左移动
+                right -= 1
+```
+（版本四）暴力法
+```python
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        for i in range(len(nums)):
+            for j in range(i+1, len(nums)):
+                if nums[i] + nums[j] == target:
+                    return [i,j]
+```
 
 Go：