I learned the X algorithm. https://blossom.primal.net/a7628d83a064a02d784826f3a4ec6a63fea68d2f6e3b8bf0fd3d6bc42a0c29b0.jpg https://blossom.primal.net/56955ab3b6d540c564d9ea15611f39b013d9866e47356b4fca...