# Python: Combine three numbers to get the target number

## Python sets: Exercise-28 with Solution

Write a Python program to find all the unique combinations of 3 numbers from a given list of numbers, adding up to a target number.

**Sample Solution:**

Python Code:

```
# Define a function 'find_combinations_of_three' that takes a list of 'nums' and a 'target_val' as input.
def find_combinations_of_three(nums, target_val):
# Convert the 'nums' list into a set to remove duplicates and then back to a list.
nums = list(set(nums))
# Create an empty set 'result' to store unique combinations of three numbers.
result = set()
# Iterate through the indices of 'nums' to consider pairs of numbers.
for i in range(len(nums)):
for j in range(i+1, len(nums)):
# Calculate the third number ('complement') needed to reach the 'target_val'.
complement = target_val - nums[i] - nums[j]
# Check if the 'complement' exists in the remaining part of the list 'nums'.
if complement in nums[:i] + nums[j+1:]:
# Add a sorted tuple of the three numbers to the 'result' set.
result.add(tuple(sorted((nums[i], nums[j], complement))))
# Convert the 'result' set into a list and return it.
return list(result)
# Define a list of numbers 'nums' and a 'target_val' for testing.
nums = [1, 2, 3, 4, 5, 6, 7, 8, 9]
target_val = 12
print("Original list of numbers:")
print(nums)
print("Target value:", target_val)
# Call the 'find_combinations_of_three' function and print the result for the given list and target value.
print("Combine three numbers whose sum equals the target number:")
print(find_combinations_of_three(nums, target_val))
# Repeat the process for a different 'target_val'.
target_val = 17
print("\nOriginal list of numbers:")
print(nums)
print("Target value:", target_val)
# Call the 'find_combinations_of_three' function and print the result for the updated target value.
print("Combine three numbers whose sum equals the target number:")
print(find_combinations_of_three(nums, target_val))
```

Sample Output:

Original list of numbers: [1, 2, 3, 4, 5, 6, 7, 8, 9] Target value: 12 Combine three numbers whose sum equal to a target number: [(1, 3, 8), (1, 4, 7), (1, 2, 9), (1, 5, 6), (3, 4, 5), (2, 3, 7), (2, 4, 6)] Original list of numbers: [1, 2, 3, 4, 5, 6, 7, 8, 9] Target value: 17 Combine three numbers whose sum equal to a target number: [(4, 5, 8), (2, 6, 9), (3, 5, 9), (2, 7, 8), (4, 6, 7), (3, 6, 8), (1, 7, 9)]

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