给定一个背包重量W和一组具有特定值val i和重量wt i的n件物品，我们需要计算可以准确构成该数量的最大数量。这与经典的背包问题不同，这里允许我们使用无限数量的物品实例。
例子：
Input : W = 100
val[] = {1, 30}
wt[] = {1, 50}
Output : 100
There are many ways to fill knapsack.
1) 2 instances of 50 unit weight item.
2) 100 instances of 1 unit weight item.
3) 1 instance of 50 unit weight item and 50
instances of 1 unit weight items.
We get maximum value with option 2.
Input : W = 8
val[] = {10, 40, 50, 70}
wt[] = {1, 3, 4, 5}
Output : 110
We get maximum value with one unit of
weight 5 and one unit of weight 3.这是一个无限的背包问题，因为我们可以使用任何资源的 1 个或多个实例。可以使用一个简单的一维数组，比如 dp[W+1]，这样 dp[i] 存储使用所有物品和 i 背包容量可以达到的最大值。请注意，我们在这里使用一维数组，这与我们使用二维数组的经典背包不同。这里的项目数量永远不会改变。我们总是有所有可用的物品。
我们可以使用以下公式递归计算 dp[]
dp[i] = 0
dp[i] = max(dp[i], dp[i-wt[j]] + val[j]
where j varies from 0
to n-1 such that:
wt[j] <= i
result = d[W]下面是上述想法的实现。
C++
// C++ program to find maximum achievable value
// with a knapsack of weight W and multiple
// instances allowed.
#include
using namespace std;
// Returns the maximum value with knapsack of
// W capacity
int unboundedKnapsack(int W, int n,
int val[], int wt[])
{
// dp[i] is going to store maximum value
// with knapsack capacity i.
int dp[W+1];
memset(dp, 0, sizeof dp);
// Fill dp[] using above recursive formula
for (int i=0; i<=W; i++)
for (int j=0; j Java
// Java program to find maximum achievable
// value with a knapsack of weight W and
// multiple instances allowed.
public class UboundedKnapsack
{
private static int max(int i, int j)
{
return (i > j) ? i : j;
}
// Returns the maximum value with knapsack
// of W capacity
private static int unboundedKnapsack(int W, int n,
int[] val, int[] wt)
{
// dp[i] is going to store maximum value
// with knapsack capacity i.
int dp[] = new int[W + 1];
// Fill dp[] using above recursive formula
for(int i = 0; i <= W; i++){
for(int j = 0; j < n; j++){
if(wt[j] <= i){
dp[i] = max(dp[i], dp[i - wt[j]] +
val[j]);
}
}
}
return dp[W];
}
// Driver program
public static void main(String[] args)
{
int W = 100;
int val[] = {10, 30, 20};
int wt[] = {5, 10, 15};
int n = val.length;
System.out.println(unboundedKnapsack(W, n, val, wt));
}
}
// This code is contributed by Aditya KumarPython3
# Python3 program to find maximum
# achievable value with a knapsack
# of weight W and multiple instances allowed.
# Returns the maximum value
# with knapsack of W capacity
def unboundedKnapsack(W, n, val, wt):
# dp[i] is going to store maximum
# value with knapsack capacity i.
dp = [0 for i in range(W + 1)]
ans = 0
# Fill dp[] using above recursive formula
for i in range(W + 1):
for j in range(n):
if (wt[j] <= i):
dp[i] = max(dp[i], dp[i - wt[j]] + val[j])
return dp[W]
# Driver program
W = 100
val = [10, 30, 20]
wt = [5, 10, 15]
n = len(val)
print(unboundedKnapsack(W, n, val, wt))
# This code is contributed by Anant Agarwal.C#
// C# program to find maximum achievable
// value with a knapsack of weight W and
// multiple instances allowed.
using System;
class UboundedKnapsack {
private static int max(int i, int j)
{
return (i > j) ? i : j;
}
// Returns the maximum value
// with knapsack of W capacity
private static int unboundedKnapsack(int W, int n,
int []val, int []wt)
{
// dp[i] is going to store maximum value
// with knapsack capacity i.
int []dp = new int[W + 1];
// Fill dp[] using above recursive formula
for(int i = 0; i <= W; i++){
for(int j = 0; j < n; j++){
if(wt[j] <= i){
dp[i] = Math.Max(dp[i], dp[i -
wt[j]] + val[j]);
}
}
}
return dp[W];
}
// Driver program
public static void Main()
{
int W = 100;
int []val = {10, 30, 20};
int []wt = {5, 10, 15};
int n = val.Length;
Console.WriteLine(unboundedKnapsack(W, n, val, wt));
}
}
// This code is contributed by vt_m.PHP
Javascript
输出：
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