Actually, Akira Kurosawa saw The Glass Key (1942), and made his own version. He even went so far as to copy/pay homage to it, with renditions of certain scenes, redone almost shot for shot in Yojimbo. For example, the captivity scene, where Yojimbo is in the brewery. He is being watched by a short thin man, and a tall fat man. They are playing a board game. They watch Yojimbo crawl across the floor, before the big man goes over, picks him up, and tosses him back in the room. This scene is taken directly from The Glass Key (down to the fact that both scenes take place in a brewery, the direction across the screen of the crawl, the sides of the table the thugs sit at... the fact that in both scenes they are playing a version of checkers, when the big one goes to pick up the hero, etc.).

Sergio Leone saw Yojimbo, and made his own version... and later got in trouble for not giving credit where credit was due.

Walter Hill saw all three, and put in nods to each of them. The bottle spin in the opening scene in Last Man Standing? That's Yojimbo throwing a stick in the air in the beginning. The dead horse in the street? That the dog with the hand in Yojimbo. The gang beating up Bruce's car? That's the mule scene from Fistful, as opposed to the initial confrontation scene from Yojimbo.

Came here to say this. And The Good, the Bad and the Ugly is Sanjuro.