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In: Computer Science

An integer n is said to be Pythagorean if there exist two nonzero integers x and...

An integer n is said to be Pythagorean if there exist two nonzero integers x and y such that x2 + y2 = n2 . Present an O(n) time algorithm to check if a given integer n is Pythagorean or not. Assume that you can nd the square root of any number in O(1) time.

Solutions

Expert Solution

def isPythagorian(n):
1. Take 2 variables, left and right.
2. initialize left with 1 and right as n.
3. While left <= right, Keep doing below:
        3.1. Find the squared sum ss of left and right as: ss = left**2 + right**2
        3.2 if ss is same as n, Then Yes, The output that given number is pythagorean and end.
        3.3 Else if ss is less than n, Then increment left by 1
        3.4 Else if ss is more than n, Then decrement right by 1.
4. Output that number is not a pythagorean number.
5. End. 

this algorithm is an O(N) algorithm, Since We take 2 variables left and right.. Left goes from 1 to N, while right goes from N to 1, till the time they do not cross each other.. Since, In each time unit, we are covering one unit towards left or to right, Hence For a number N, it is a O(N) algorithm.

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