46 lines
1.3 KiB
Python
46 lines
1.3 KiB
Python
"""
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A non-empty array A consisting of N integers is given. The array
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contains an odd number of elements, and each element of the array can
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be paired with another element that has the same value, except for one
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element that is left unpaired.
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For example, in array A such that:
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A[0] = 9 A[1] = 3 A[2] = 9
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A[3] = 3 A[4] = 9 A[5] = 7
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A[6] = 9
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the elements at indexes 0 and 2 have value 9,
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the elements at indexes 1 and 3 have value 3,
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the elements at indexes 4 and 6 have value 9,
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the element at index 5 has value 7 and is unpaired.
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Write a function:
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def solution(A)
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that, given an array A consisting of N integers fulfilling the above
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conditions, returns the value of the unpaired element.
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For example, given array A such that:
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A[0] = 9 A[1] = 3 A[2] = 9
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A[3] = 3 A[4] = 9 A[5] = 7
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A[6] = 9
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the function should return 7, as explained in the example above.
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Write an efficient algorithm for the following assumptions:
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N is an odd integer within the range [1..1,000,000];
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each element of array A is an integer within the range [1..1,000,000,000];
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all but one of the values in A occur an even number of times.
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"""
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def solution(A):
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s = set()
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for x in A:
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if x in s:
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s.remove(x)
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else:
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s.add(x)
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return s.pop()
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