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1). Pattern will visit point (17,18) immediately after (18,17).
as you can see in every straight line which is making 135 degree with x-axis has sum of co-ordiantes of each point is either odd or even. when sum is odd pattern is going downwards.
now, 17+18 = 35 which is odd it indicates next point will be
x = 17+1 = 18, y = 18-1=17

2). it will visit 74 points before the route reaches the point (9,4).
total point = 11*12/2 + 8 = 74