Alpha-beta pruning

  function alphabeta(node, depth, α, β, maximizingPlayer)
       if depth =  or node is a terminal node
           return the heuristic value of node
       if maximizingPlayer
           v := -∞
           for each child of node
               v := max(v, alphabeta(child, depth - , α, β, FALSE))
               α := max(α, v)
               if β ≤ α
                   break (* β cut-off *)
           return v
       else
           v := ∞
           for each child of node
               v := min(v, alphabeta(child, depth - , α, β, TRUE))
               β := min(β, v)
               if β ≤ α
                   break (* α cut-off *)
          return v

来自https://en.wikipedia.org/wiki/Alpha–beta_pruning