How to Fix Product of Array Except Self Errors

In this tutorial, you'll learn about How to Fix Product of Array Except Self Errors. We cover key concepts, practical examples, and best practices.

Fix product of array except self errors when division creates zero errors or prefix-suffix overflows.

Quick Fix

Wrong

def product_except_self(n):
    t=1
    for x in n: t*=x
    return [t//x for x in n]

Division by zero when element is 0. Multiple zeros give wrong results.

Right

def product_except_self(n):
    l=[1]*len(n); p=1
    for i in range(len(n)): l[i]=p; p*=n[i]
    s=1
    for i in range(len(n)-1,-1,-1): l[i]*=s; s*=n[i]
    return l

[1,2,3,4] -> [24,12,8,6]. [-1,1,0,-3,3] -> [0,0,9,0,0]. O(n).

Prevention

Never use division. Prefix product left-to-right, suffix right-to-left.

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