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combinationSum3_216.py
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combinationSum3_216.py
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#!/usr/bin/env python
# coding=utf-8
class Solution(object):
def combinationSum3(self, k, n):
"""
:type k: int
:type n: int
:rtype: List[List[int]]
"""
if k < 1 or n < 1:
return []
elif k == 1:
return [[n]]
if k >= n or k * 9 <= n:
return []
solutions = []
partial = []
self.backtracking(solutions, partial, k, n, 1)
return solutions
def backtracking(self, solutions, partial, k, n, number):
if n == 0 and k == 0:
solutions.append(partial[:])
return
elif n == 0 and k > 0:
return
elif n > 0 and k == 0:
return
elif number > 9 or number > n:
return
else:
partial.append(number)
self.backtracking(solutions, partial, k - 1, n - number, number + 1)
partial.pop()
self.backtracking(solutions, partial, k, n, number + 1)