Contribute/subset-sum-problem-osum-space.py at main · Shalton2005/Contribute · GitHub

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# Returns true if there exists a subset
# with given sum in arr[]

def isSubsetSum(arr, n, sum):

	# The value of subset[i%2][j] will be true
	# if there exists a subset of sum j in
	# arr[0, 1, ...., i-1]
	subset = [ [False for j in range(sum + 1)] for i in range(3) ]

	for i in range(n + 1):
		for j in range(sum + 1):
			# A subset with sum 0 is always possible
			if (j == 0):
				subset[i % 2][j] = True

			# If there exists no element no sum
			# is possible
			else if (i == 0):
				subset[i % 2][j] = False
			else if (arr[i - 1] <= j):
				subset[i % 2][j] = subset[(i + 1) % 2][j - arr[i - 1]] or subset[(i + 1)
																			% 2][j]
			else:
				subset[i % 2][j] = subset[(i + 1) % 2][j]

	return subset[n % 2][sum]

# Driver code
arr = [ 6, 2, 5 ]
sum = 7
n = len(arr)
if (isSubsetSum(arr, n, sum) == True):
	print ("There exists a subset with given sum")
else:
	print ("No subset exists with given sum")