# Python | Find all triplets in a list with given sum

Given a list of integers, write a Python program to find all triplets that sum up to given integer ‘k’.

Examples:

```Input : [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], k = 10
Output : [(1, 5, 4), (1, 6, 3), (1, 7, 2), (2, 5, 3)]

Input : [12, 3, 6, 1, 6, 9], k = 24
Output : [(12, 6, 6), (12, 9, 3)]
```

Approach #1 : Naive (Using set)
In this approach, we use two for loops. The first loop sets first element, another to check whether other two elements including first sums up to k or not. This approach takes O(n2) time complexity.

 `# Python3 program to Find total number  ` `# of triplets in a temp_list with given k ` ` `  `def` `findTriplets(lst, k): ` `    ``triplet_count ``=` `0` `    ``final_temp_list ``=``[] ` `     `  `    ``for` `i ``in` `range``(``0``, ``len``(lst)``-``1``):  ` `         `  `        ``s ``=` `set``()  ` `        ``temp_list ``=` `[] ` ` `  `        ``# Adding first element ` `        ``temp_list.append(lst[i]) ` ` `  `        ``curr_k ``=` `k ``-` `lst[i]  ` `         `  `        ``for` `j ``in` `range``(i ``+` `1``, ``len``(lst)):  ` `             `  `            ``if` `(curr_k ``-` `lst[j]) ``in` `s:  ` `                ``triplet_count ``+``=` `1` `                 `  `                ``# Adding second element ` `                ``temp_list.append(lst[j]) ` ` `  `                ``# Adding third element ` `                ``temp_list.append(curr_k ``-` `lst[j]) ` `                 `  `                ``# Appending tuple to the final list ` `                ``final_temp_list.append(``tuple``(temp_list)) ` `                ``temp_list.pop(``2``) ` `                ``temp_list.pop(``1``) ` `            ``s.add(lst[j]) ` `             `  `    ``return` `final_temp_list ` `     `  `# Driver Code ` `lst ``=` `[``1``, ``2``, ``3``, ``4``, ``5``, ``6``, ``7``, ``8``, ``9``, ``10``] ` `k ``=` `10` `print``(findTriplets(lst, k)) `

Output:
```[(1, 5, 4), (1, 6, 3), (1, 7, 2), (2, 5, 3)]
```

Approach #2 : Using itertools
Python itertools module provide combination(iterable, r) function. This tool returns the r length subsequences of elements from the input iterable. Every time we make a combination of 3 elements and check if they sums up to k or not.

 `# Python3 program to Find total number  ` `# of  triplets in a list with given sum ` `from` `itertools ``import` `combinations ` ` `  `def` `findTriplets(lst, key): ` `     `  `    ``def` `valid(val): ` `        ``return` `sum``(val) ``=``=` `key ` `         `  `    ``return` `list``(``filter``(valid, ``list``(combinations(lst, ``3``)))) ` ` `  `# Driver Code ` `lst ``=` `[``1``, ``2``, ``3``, ``4``, ``5``, ``6``, ``7``, ``8``, ``9``, ``10``] ` `print``(findTriplets(lst, ``10``)) `

Output:
```[(1, 2, 7), (1, 3, 6), (1, 4, 5), (2, 3, 5)]
```

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