C++ Check diagonally from 2d array - c++

Question

Beginner at c++ here.
for (int z = 0; z < arraysize; z++) {
if (generated[z][0] == generated[z][1] && generated[z][1] == generated[z][2]) {
wins++;
}
if (generated[0][z] == generated[1][z] && generated[1][z] == generated[2][z]) {
wins++;
}
As you can see it checks for the horizontal lines. I would like to check wether or not there are 3 in a row diagonally. If there is, the wins variable should add one. Any ideas?

Answer 1

You can do this by using z as the index for both extents instead of just one.
for (int z = 0; z < arraysize; z++)
{
if (generated[z][z] == generated[0][0])
{
//... handle it
}
if (generated[arraysize - z - 1][z] == generated[arraysize - 1][0])
{
//... handle it
}
}
Unfortunately this will only get you so far. The current logic in your code is not going to work as you expect. The problem is that it keeps a cumulative count of matches across all lines both horizontally and vertically. If you have several partial matches you could end up with a an incorrect win value. You can avoid this problem by adding a couple of additional loops to check the contents of each the vertical and horizontal lines as you perform your scan. This will require a couple of additional flags to be added as well to keep track of whether there is a win in either direction. The following example should provide you with a much more flexible set of checks that are flexible and can be used for any size array.
bool hwin = false;
bool vwin = false;
int d1wins = 0;
int d2wins = 0;
for (int z = 0; z < arraysize; z++)
{
int hwins = 0;
int vwins = 0;
// Check horizontal line
for (int i = 0; i < arraysize; ++i)
{
if (generated[i][z] == generated[0][z])
{
hwins++;
}
}
hwin = hwin || hwins == arraysize;
// Check vertical line
for (int i = 0; i < arraysize; ++i)
{
if (generated[z][i] == generated[z][0])
{
vwins++;
}
}
vwin = vwin || vwins == arraysize;
// Check diagonal
if (generated[z][z] == generated[0][0])
{
d1wins++;
}
// Check diagonal
if (generated[arraysize - z - 1][z] == generated[arraysize - 1][0])
{
d2wins++;
}
}
bool dwin = d1wins == arraysize || d2wins == arraysize;

Answer 2

From two if condition, you used, I think you are trying something like 3*3 Tic-tac-toe.
So, if your arraysize is 3, you can't use following checking in your loop:
if (generated[z][z] == generated[z+1][z+1] && generated[z+1][z+1] == generated[z+2][z+2])
{
wins++;
}
z+2 and z+1 will cross the array limit.
So you can check it outside of your loop:
generated[0][0] == generated[1][1] && generated[1][1] == generated[2][2]
generated[0][2] == generated[1][1] && generated[1][1] == generated[2][0]