Factor Combinations — LeetCode 254 Python Solution

The problem

Numbers can be regarded as the product of their factors. For example, 8 = 2 x 2 x 2 = 2 x 4.

Example

Input

n = 1

Output

[]

Python solution

class Solution:
    def getFactors(self, n: int) -> List[List[int]]:
        def dfs(n, i):
            if t:
                ans.append(t + [n])
            j = i
            while j * j <= n:
                if n % j == 0:
                    t.append(j)
                    dfs(n // j, j)
                    t.pop()
                j += 1

        t = []
        ans = []
        dfs(n, 2)
        return ans

Complexity

Pattern: Backtracking

Build candidates one choice at a time and abandon a branch the moment it cannot work. LeetCode 254. Factor Combinations is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Backtracking.

The backtracking guide has the Python template for the pattern and the 105 LeetCode problems that use it.

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