了解分数背包，数组和指针

Question

Just started learning C programming and decided to take a class in algorithmic Toolbox on Coursera. One of the challenges is writing a code using fractional knapsack, maximizing the value of loot and a pseudo code was given to help in coding the solution. Below are the pseudo code and the code I wrote for the pseudo code.

#include<stdio.h>

int min(int a, int b)
{
    if (a < b)
        return a;
    else
        return b;
}

int knapsack(int value[], int weight[])
{
    int capacity = 100;
    int val = 0;
    int array[] = { 0 };
    for (int i = 1; i < capacity; i++)
    {
        if (capacity == 0)
        {
            return val;
        }
        for (int i = 1; i < capacity; i++)
        {
            if (weight[i] > 0 && (value[i] / weight[i]))
            {
                int a = min(weight[i], capacity);
                val = val + a * (value[i] / weight[i]);
                weight[i] = weight[i] - a;
                array[i] = array[i] + a;
                capacity = capacity - a;
            }
        }
    }
    return val;
}

int main()
{
    int value[100];
    int weight[100];
    scanf("%d", &value[100]);
    scanf("%d", &weight[100]);
    printf("%d", knapsack(value[100], weight[100]));
    return 0;
}

pseudo code

Knapsack(W, w1,v1,......wn,vn)
A <-- [0,0,], V <-- 0;
repeat n times:
if W =  0:
return (V,A)
select i with Wi > 0 and max vi/wi
a <-- min(wi, W)
V <-- V + a(vi/wi)
wi <-- wi - a, A[i] <-- A[i] + a, W <-- W - a
return (V, A)

I am getting errors when I compile such as "passing argument 1 of 'knapsack' makes pointer from integer without a cast [-Wint-conversion]"

printf("%d", knapsack(value[100],weight[100]));

"expected int * but argument is of type 'int'"

int knapsack(int value[], int weight[])

I also want to know if it is a good practice to declare int value[], int weight[] in the function int knapsack argument and also more explanation in using arrays and pointers in situations like this.

Answer 1

int knapsack(int value[], int weight[])

The above statement gives the compiler the information about HOW the function should be called (type of arguments) and WHAT the function will return.

1. It says the function knapsack will return an integer value (the 1st int).

2. Its name is knapsack (case-sensitive).

3. It expects two arguments: an integer array (named value) and an integer array (named weight).

Points 1, 2 and 3 together make up the signature of a function.

To call the function you have to pass 2 integer arrays as its arguments.

The mistake : value[100] corresponds to an INTEGER ENTRY in the array and not the array itself.

To pass the array you should pass the array name as its argument, which your function expects.

Call the function like this: knapsack(value, weight)

value corresponds the array value and weight corresponds to the array weight

Also, passing value[100] corresponds to some garbage value that is not within the array bounds as you can only access elements ranging from value[0] to value[99] (0-based indexing).