mablatnik / algorithmic-toolbox Goto Github PK

Hi,

With regards to week1/max_pairwise_product.py
would you please explain what does "if max_index1 == -1" do in the if condition in the for loop?

since max_index1 is initially assigned to -1, why do we need that in the if loop again? I did test it and knew that the answer wouldn't be right without that condition, but I can't figure out why.
Thanks!

Wrong answers

    **Just add this code, the previous code exceeds the time**

#include
#include
#include

using std::cin;
using std::cout;
using std::vector;

long long MaxPairwiseProduct(const vector &numbers)
{
long long result = 0;
int n = numbers.size();
for (int i = 0; i < n; ++i)
{
for (int j = i + 1; j < n; ++j)
{
if (((long long)(numbers[i])) * numbers[j] > result)
{
result = ((long long)(numbers[i])) * numbers[j];
}
}
}
return result;
}

long long MaxPairwiseProductFast(const vector &numbers)
{
int n = numbers.size();

int max_index1 = -1;
for (int i = 0; i < n; ++i)
    if ((max_index1 == -1) || (numbers[i] > numbers[max_index1]))
        max_index1 = i;

int max_index2 = -1;
for (int j = 0; j < n; ++j)
    if ((j != max_index1) && ((max_index2 == -1) || (numbers[j] > numbers[max_index2])))
        max_index2 = j;

return ((long long)(numbers[max_index1])) * numbers[max_index2];

}

int main()
{
int n;
cin >> n;
vector numbers(n);
for (int i = 0; i < n; ++i)
{
cin >> numbers[i];
}

long long result = MaxPairwiseProductFast(numbers);
cout << result << "\n";
return 0;

}

Originally posted by @maayaankk in #6 (comment)

Your week 3 largest number is nowhere even closer to the actual solution, so many syntax and semantic mistakes are there. I suggest correct it.