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POMin and Max of a List in Python (without using min/max function)
 

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  1. POMin and Max of a List in Python (without using min/max function)
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    <p>I was wondering if there is a way to find min &amp; max of a list without using min/max functions in Python. So i wrote a small code for the same using recursion. My logic is very naive: I make two stacks (min_stack and max_stack) which keep track of minimum and maximum during each recursive call. I have two questions: </p> <ol> <li>Could somebody help me estimate the complexity of my code?</li> <li>Is there a better way to do this? Will sorting the list using mergesort/quicksort and picking up first and last element give a better performance?</li> </ol> <p>Thank you</p> <p>Here is my attempt in Python: </p> <pre><code>minimum = [] maximum = [] # Defining Stack Class class Stack: def __init__(self) : self.items = [] def push(self, item) : self.items.append(item) def pop(self) : return self.items.pop() def access(self, index): return self.items[index] def isEmpty(self) : return (self.items == []) def length(self): return len(self.items) def minmax(input_list): # make two stacks, one for min and one for max min_stack = Stack() max_stack = Stack() # comparing the first two elements of the list and putting them in appropriate stack if input_list[0]&lt;input_list[1]: min_stack.push(input_list[0]) max_stack.push(input_list[1]) else: max_stack.push(input_list[0]) min_stack.push(input_list[1]) # Pushing remaining elements of the list into appropriate stacks. for i in range(2, len(input_list)): if input_list[i] &lt; min_stack.access(-1): min_stack.push(input_list[i]) else: max_stack.push(input_list[i]) # to find minimum minlist = [] while min_stack.length() &gt; 0: minlist.append(min_stack.pop()) # to find maximum maxlist = [] while max_stack.length() &gt; 0: maxlist.append(max_stack.pop()) if len(minlist) &gt; 1: minmax(minlist) else: minimum.append(minlist) if len(maxlist) &gt; 1: minmax(maxlist) else: maximum.append(maxlist) def main(): input_list = [2, 0, 2, 7, 5, -1, -2] print 'Input List is: ', input_list minmax(input_list) print 'Global Minimum is: ', minimum[0] print 'Global Maximum is: ', maximum[len(maximum)-1] if __name__ == "__main__": main() </code></pre>
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    1. USPrakhar Mehrotra
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    1. COwow... That seems really overly complex ...
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      1. POMin and Max of a List in Python (without using min/max function)
      1. USmgilson
    2. COI would assume using sorted and taking the 0 and -1 indexes will be faster ... and much more readable `a = sorted(my_list);min,max=a[0],a[-1];` If I was an interviewer and asked this question ... the canidate who handed in what you have would not get the job...
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      1. POMin and Max of a List in Python (without using min/max function)
      1. USJoran Beasley
    3. CO@mgilson: yeah...its complex because I was asked to implement it using Stacks as a way of exercise.
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      1. POMin and Max of a List in Python (without using min/max function)
      1. USPrakhar Mehrotra
 

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