Given two integers n and k, return all possible combinations of k numbers chosen from the range [1, n].You may return the answer in any order. Example 1:Input: n = 4, k = 2Output: [[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]]Explanation: There are 4 choose 2 = 6 total combinations.Note that combinations are unordered, i.e., [1,2] and [2,1] are considered to be the same combination.Example 2:Input: n = 1, k = 1Output: [[1]]Explanation: There is 1 choose 1 = 1 total combination. Constraints:1 <= n <= 201 <= k <= n
Question
Given two integers n and k, return all possible combinations of k numbers chosen from the range [1, n].You may return the answer in any order. Example 1:Input: n = 4, k = 2Output: [[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]]Explanation: There are 4 choose 2 = 6 total combinations.Note that combinations are unordered, i.e., [1,2] and [2,1] are considered to be the same combination.Example 2:Input: n = 1, k = 1Output: [[1]]Explanation: There is 1 choose 1 = 1 total combination. Constraints:1 <= n <= 201 <= k <= n
Solution
This problem can be solved using a recursive approach. Here are the steps:
-
Create a function
combinethat takes two parametersnandk. -
Initialize an empty list
resultto store the combinations. -
Create a helper function
dfsthat takes three parameters:start,path, andk. This function will perform a depth-first search to find all combinations.startis the starting point for the combination.pathis the current combination.kis the number of elements in the combination.
-
In the
dfsfunction, check ifkis 0. If it is, appendpathtoresultand return. -
If
kis not 0, loop fromstartton. For eachiin the loop, calldfswithi + 1,path + [i], andk - 1. -
Call the
dfsfunction with1,[], andk. -
Return
result.
Here is a Python code snippet that implements these steps:
def combine(n, k):
result = []
def dfs(start, path, k):
Similar Questions
Given an array of integers arr, the length of the array n, and an integer k, find all the unique combinations in arr where the sum of the combination is equal to k. Each number can only be used once in a combination.Example 1:Input: n = 5, k = 7arr[] = { 1, 2, 3, 3, 5 }Output:{ { 1, 3, 3 }, { 2, 5 } }Explanation:1 + 3 + 3 = 72 + 5 = 7
Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order. Example 1:Input: nums = [1,2,3]Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]Example 2:Input: nums = [0,1]Output: [[0,1],[1,0]]Example 3:Input: nums = [1]Output: [[1]] Constraints:1 <= nums.length <= 6-10 <= nums[i] <= 10All the integers of nums are unique.
bool combinations( int array[ ], int size, int target ); - Returns true if the total of any combination of elements in the array parameter equals the target value. In determining combinations, each element value should only be used once. For array of {2, 3, 4}, you could build target values of only 2, 3, 4, 5 (2+3), 6 (2+4), 7 (3+4) or 9 (2+3+4) only and not 12 (3+3+3+3) or 16 (4+4+4+4).
Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.
You are given an integer array nums of size n and a positive integer k.Divide the array into one or more arrays of size 3 satisfying the following conditions:Each element of nums should be in exactly one array.The difference between any two elements in one array is less than or equal to k.Return a 2D array containing all the arrays. If it is impossible to satisfy the conditions, return an empty array. And if there are multiple answers, return any of them.
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