Add figures to replace_linear_by_hashing.md

codes/python/chapter_searching/two_sum.py

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+"""
+File: two_sum.py
+Created Time: 2022-11-25
+Author: Krahets (krahets@163.com)
+"""
+
+
+def two_sum_brute_force(nums: list[int], target: int) -> list[int]:
+    """方法一：暴力枚举"""
+    # 两层循环，时间复杂度 O(n^2)
+    for i in range(len(nums) - 1):
+        for j in range(i + 1, len(nums)):
+            if nums[i] + nums[j] == target:
+                return [i, j]
+    return []
+
+
+def two_sum_hash_table(nums: list[int], target: int) -> list[int]:
+    """方法二：辅助哈希表"""
+    # 辅助哈希表，空间复杂度 O(n)
+    dic = {}
+    # 单层循环，时间复杂度 O(n)
+    for i in range(len(nums)):
+        if target - nums[i] in dic:
+            return [dic[target - nums[i]], i]
+        dic[nums[i]] = i
+    return []
+
+
+"""Driver Code"""
+if __name__ == "__main__":
+    # ======= Test Case =======
+    nums = [2, 7, 11, 15]
+    target = 13
+
+    # ====== Driver Code ======
+    # 方法一
+    res: list[int] = two_sum_brute_force(nums, target)
+    print("方法一 res =", res)
+    # 方法二
+    res: list[int] = two_sum_hash_table(nums, target)
+    print("方法二 res =", res)