LeetCode September Challenge(Day-12)

leetcode monthly challenge

Topic — Combination Sum III

Q. Find all valid combinations of k numbers that sum up to n such that the following conditions are true:

• Only numbers 1 through 9 are used.
• Each number is used at most once.

Return a list of all possible valid combinations. The list must not contain the same combination twice, and the combinations may be returned in any order.

Example 1:

Input: k = 3, n = 7
Output: [[1,2,4]]
Explanation:
1 + 2 + 4 = 7
There are no other valid combinations.

Example 2:

Input: k = 3, n = 9
Output: [[1,2,6],[1,3,5],[2,3,4]]
Explanation:
1 + 2 + 6 = 9
1 + 3 + 5 = 9
2 + 3 + 4 = 9
There are no other valid combinations.

Example 3:

Input: k = 4, n = 1
Output: []
Explanation: There are no valid combinations. [1,2,1] is not valid because 1 is used twice.

Example 4:

Input: k = 3, n = 2
Output: []
Explanation: There are no valid combinations.

Example 5:

Input: k = 9, n = 45
Output: [[1,2,3,4,5,6,7,8,9]]
Explanation:
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 45
​​​​​​​There are no other valid combinations.

Constraints:

• 2 <= k <= 9
• 1 <= n <= 60

Logic:

• In python there is a in-built method called “combinations()” under itertools which print all possible combinations of n-elements in array
• Use the above method to find all the possible combinations. The result will be in array
• Iterate this array and find the sum of the list of combinations which equals “n” and move it to a empty list array.
• That’s it

Code:

code

Happy Coding!!!

Here is the leetcode link:
https://leetcode.com/explore/challenge/card/september-leetcoding-challenge/555/week-2-september-8th-september-14th/3457/

Please feel free to comment, if you have any problem or doubt.

Thank You!!!
Never settle and always Hustle!!!
☺
-Gareeb CODER

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