Python for maximum pairwise product
<pre><code>n = int(input("Enter the number of elements in the array (2-200,000):"))
a = [int(x) for x in input("Enter all numbers of the sequence with only non-negative intergers not exceeding 100,000:").split()]
c = list()3

for i in range(0,n):
    for j in range (1,n):
        if a[i] != a[j]:
            m = a[i]*a[j]
            c.append(m)
        else:
            continue
print(max(c))
</code></pre>

<p>This code works. However, I want to define a function to automatically calculating the max product from the 5th line in the code shown below.</p>

<pre><code>def MaxPairwiseProduct(n,a,c):
for i in range(0,n):
    for j in range (1,n):
        if a[i] != a[j]:
            m = a[i]*a[j]
            c.append(m)
        else:
            continue

        Product = max(c)

        return Product

n = int(input("Enter the number of elements in the array (2-200,000):"))
a = [int(x) for x in input("Enter all numbers of the sequence with only non-negative intergers not exceeding 100,000:").split()]
c = list()
MaxPairwiseProduct(n,a,c)
</code></pre>

<p>I re-write the function but it does not work. It reveals "IndentationError: expected an indented block"</p>

<pre><code># Uses python3
def MaxPairwiseProduct(n,a,c):
    for i in range(0,n):
        for j in range (1,n):
            if a[i] != a[j]:
                m = a[i]*a[j]
                c.append(m)

            else:
                continue

    Product1 = max(c)
    return Product1

def MaxPairwiseProductFast(n,a):
    max_index1 = -1
    for i in range(0,n):
        if a[i] &gt; a[max_index1]:
            max_index1 = i
        else:
            continue

    max_index2 = -1
    for j in range(0,n):
        if a[j] &gt; a[max_index2] and a[j] != a[max_index1]:
            max_index2 = j   
        else:
            continue

    Product2 = a[max_index1]*a[max_index2]
    return Product2

n = int(input("Enter the number of elements in the array (2-200,000):"))
a = [int(x) for x in input("Enter all numbers of the sequence with only non-negative intergers not exceeding 100,000:").split()]
c = list()

print('The max value by regular algorithm:', MaxPairwiseProduct(n,a,c))
print('The max value by faster algorithm:', MaxPairwiseProductFast(n,a))  
</code></pre>

<p>This code contains the second algorithm to calculate the max value.</p>

python product