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| 1 | +The following is a Python implementation of the 0-1 knapsack problem with memorization: |
| 2 | + |
| 3 | +def knapsack_memorization(weights, values, capacity): |
| 4 | + """Solves the 0-1 knapsack problem using memorization. |
| 5 | + |
| 6 | + Args: |
| 7 | + weights: A list of weights of the items. |
| 8 | + values: A list of values of the items. |
| 9 | + capacity: The capacity of the knapsack. |
| 10 | + |
| 11 | + Returns: |
| 12 | + The maximum value of the items that can be placed in the knapsack. |
| 13 | + """ |
| 14 | + |
| 15 | + memo = {} |
| 16 | + |
| 17 | + def knapsack_helper(i, capacity): |
| 18 | + if i == 0 or capacity == 0: |
| 19 | + return 0 |
| 20 | + |
| 21 | + key = (i, capacity) |
| 22 | + if key in memo: |
| 23 | + return memo[key] |
| 24 | + |
| 25 | + if weights[i - 1] > capacity: |
| 26 | + max_value = knapsack_helper(i - 1, capacity) |
| 27 | + else: |
| 28 | + max_value = max(knapsack_helper(i - 1, capacity), |
| 29 | + values[i - 1] + knapsack_helper(i - 1, capacity - weights[i - 1])) |
| 30 | + |
| 31 | + memo[key] = max_value |
| 32 | + return max_value |
| 33 | + |
| 34 | + return knapsack_helper(len(weights), capacity) |
| 35 | + |
| 36 | + |
| 37 | + |
| 38 | +The following is a Python implementation of the 0-N knapsack problem: |
| 39 | + |
| 40 | +def knapsack_0_n(weights, values, capacity): |
| 41 | + """Solves the 0-N knapsack problem. |
| 42 | + |
| 43 | + Args: |
| 44 | + weights: A list of weights of the items. |
| 45 | + values: A list of values of the items. |
| 46 | + capacity: The capacity of the knapsack. |
| 47 | + |
| 48 | + Returns: |
| 49 | + The maximum value of the items that can be placed in the knapsack. |
| 50 | + """ |
| 51 | + |
| 52 | + memo = {} |
| 53 | + |
| 54 | + def knapsack_helper(i, capacity): |
| 55 | + if i == 0 or capacity == 0: |
| 56 | + return 0 |
| 57 | + |
| 58 | + key = (i, capacity) |
| 59 | + if key in memo: |
| 60 | + return memo[key] |
| 61 | + |
| 62 | + max_value = 0 |
| 63 | + for j in range(1, capacity // weights[i - 1] + 1): |
| 64 | + max_value = max(max_value, values[i - 1] * j + knapsack_helper(i - 1, capacity - weights[i - 1] * j)) |
| 65 | + |
| 66 | + memo[key] = max_value |
| 67 | + return max_value |
| 68 | + |
| 69 | + return knapsack_helper(len(weights), capacity) |
| 70 | + |
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