41 lines
972 B
Crystal
41 lines
972 B
Crystal
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class Array(T)
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def knapsack(budget, &cv : T -> {Int32,Int32})
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cost_values = map &cv
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memo = {} of {Int32, Int32} => Int32
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bt = {} of {Int32, Int32} => Bool
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compute = uninitialized Int32, Int32 -> Int32
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compute = ->(size : Int32, budget : Int32) {
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if m = memo[{size, budget}]?
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return m
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end
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return memo[{size, budget}] = 0 if size == 0
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cost, value = cost_values[size-1]
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no_val = compute.call(size-1, budget)
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yes_val = (budget < cost) ? 0 : compute.call(size-1, budget - cost) + value
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if yes_val > no_val
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bt[{size, budget}] = true
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return yes_val
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else
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bt[{size, budget}] = false
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return no_val
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end
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}
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value = compute.call(size, budget)
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i = size
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items = [] of T
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puts bt
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while i != 0
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if bt[{i, budget}]
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items << self[i-1]
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budget -= cost_values[i-1][0]
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end
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i -= 1
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end
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{value, items}
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end
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end
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