Given an integer array with all positive numbers and no duplicates, find the number of possible combinations that add up to a positive integer target.
Example:
nums = [1, 2, 3]
target = 4
The possible combination ways are:
(1, 1, 1, 1)
(1, 1, 2)
(1, 2, 1)
(1, 3)
(2, 1, 1)
(2, 2)
(3, 1)
Note that different sequences are counted as different combinations.
Therefore the output is 7.
class Solution:
def combinationSum4(self, nums, target):
dp = [0] * (target + 1)
dp[0] = 1
for i in range(target+1):
for j in nums:
if i < j:
continue
dp[i] += dp[i-j]
return dp[-1]