Check if character rotation is 180 degree turn

I've been struggling with this issue for a while now and I have no idea how to fix it.

I want to check if my character would turn 180 degrees and if it would, then don't turn. So basically only make it turn 90 degrees. the solution i tried works perfectly when i press a button on the vertical axis but for some reason it doesn't want to work on the horizontal axis whatever I try.

This is the code I have. on the horizontal axis the angles when left and right is -90 and 90 and on the vertical axis it's 0 and 180.

If anyone could help me in any way... I am out of ideas on how to fix it.

 if( horizontalInput==1 )
 {
     //-90 & 90
     Debug.Log("previouslocation" + controller.transform.rotation.eulerAngles.y);
 
     if (controller.transform.rotation.y == 90 )
         Debug.Log("180 degree +h turn");
     else
     {
         Debug.Log("previouslocation" + controller.transform.rotation.eulerAngles.y);
         controller.transform.rotation = rotation;
     }
 }
 else if (horizontalInput == -1)
 {
     Debug.Log("previouslocation" + controller.transform.rotation.eulerAngles.y);
 
     if (controller.transform.rotation.y == 270)
         Debug.Log("180 degree -h turn");
     else
     {
         Debug.Log("previouslocation" + controller.transform.rotation.eulerAngles.y);
         controller.transform.rotation = rotation;
     }
 }
 else if (verticalInput == 1)
 {
     //0 & 180
     Debug.Log("previouslocation" + controller.transform.rotation.eulerAngles.y);
     
     if (controller.transform.rotation.eulerAngles.y == 180)
         Debug.Log("180 degree +v turn");
     else
         controller.transform.rotation = rotation;
 }
 else if(verticalInput == -1)
 {
     Debug.Log("previouslocation" + controller.transform.rotation.eulerAngles.y);
 
     if (controller.transform.rotation.eulerAngles.y <= 0)
         Debug.Log("180 degree -v turn");
     else
         controller.transform.rotation = rotation;
 }