377. Combination Sum IV.py

# 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.
# Follow up:
# What if negative numbers are allowed in the given array?
# How does it change the problem?
# What limitation we need to add to the question to allow negative numbers?

# Credits:
# Special thanks to @pbrother for adding this problem and creating all test cases.
class Solution(object):
    def combinationSum4(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        dp = [1] + [0] * target
        for i in range(1,target+1):
            for num in nums:
                if i >= num:
                    dp[i] += dp[i-num]
            print dp
        return dp[target]