004. Sum of two numbers(Hash and enumerate)

# Sum of two numbers
# A: Hash (Dictionary)
def two_sum (nums,target):
    num_dict = {}  # Create a dictionary to store elements and their indices
    for i, num in enumerate(nums):
        complement = target - num # Calculate another number needed
        if complement in num_dict:  # If another number is found in the dictionary, return their index
            return [num_dict[complement], i]
        else:
            num_dict[num] = i
    
    return ()

nums = [2, 7, 11, 15]
target = 26
print(two_sum(nums,target))

# Example
nums = [2, 7, 11, 15]
target=26
result = two_sum(nums, target)
print(result) # Output: [2, 3]

# B: Mine method:
# Error: Trying to use for j in lst[i:] in a nested loop, this is not the correct approach. In this context, i is an element in the list list_1, not an index, so writing lst[i:] causes an error.
def find_add(lst):
     aim = input()
     aim = int(aim)
     lst_len = len(lst)
     for i in lst:
         for j in lst[i:]:
             if i + j == aim:
                 index_1 = lst.index(i)
                 index_2 = lst.index(j)
     return index_1, index_2



list_1 = (1,2,3,4,5,6,7,8)
find_add(list_1)

# correct:
def find_add(lst):
     aim = input()
     aim = int(aim)
     lst_len = len(lst)
     index_1 = -1 #The initial index is -1, indicating that no matching element was found
     index_2 = -1

     for i in range(lst_len):
         for j in range(i + 1, lst_len):
             if lst[i] + lst[j] == aim:
                 index_1 = i
                 index_2 = j
                 break
         if index_1 != -1:
             break # If a matching element is found, exit the outer loop

     return index_1, index_2

list_1 = [1, 5, 7, 10]
result = find_add(list_1)
print(result)