#include <iostream>
using namespace std;
int main()
{
int ile;
cin >> ile;
for (int a = 0; a < ile; a++)
{
int szerokosc, max_wysokosc;
int pojemnosc = 0;
cin >> szerokosc;
int* wysokosc;
wysokosc = new int[szerokosc];
for (int i = 0; i < szerokosc; i++)
{
cin >> wysokosc[i];
}
if (wysokosc[0] < wysokosc[szerokosc - 1])
{
max_wysokosc = wysokosc[0];
}
else if (wysokosc[0] > wysokosc[szerokosc - 1])
{
max_wysokosc = wysokosc[szerokosc - 1];
}
else max_wysokosc = wysokosc[0];
for (int j = 1; j < szerokosc - 1; j++)
{
if (max_wysokosc < wysokosc[j])
{
continue;
}
else
pojemnosc += max_wysokosc - wysokosc[j];
}
cout << pojemnosc << endl;
}
return 0;
}
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