N-Queens II[Hard]

N-Queens II[Hard]_第1张图片

这题感觉比N-Queen I 还简单啊。。

Diagonals 的size 为 2*n 引人深思啊。

45 degree line is y = x + b

135 degree line is y = -x + b

in another word, 45 degree y - x is constant, and 135 degree y + x is constant.

Here b is shifted to [0~2n), so y-x and y+x can be trackable.

N-Queens II[Hard]_第2张图片

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