How to read from scanf values of the 01-knapsack algorithm and pass to a function - knapsack-problem

Question

If I enter the numbers:
3 10
7 6
5 5
4 5
the output is : 9. OK — that's the correct value. But if I enter:
10 25
3 5
3 5
3 5
3 5
3 5
3 5
3 5
3 5
3 5
3 5
the correct output should be: 15 but I receive 2005985278.
What's the problem in this code?
#include<stdio.h>
#include<stdlib.h>
#define MA 29
int max(int a, int b) {
return (a > b)? a : b;
}
int knapsack(int W, int P[], int V[], int N)
{
int i, w;
int K[N+1][W+1];
for (i = 0; i <= N; i++)
{
for (w = 1; w <= W; w++)
{
if (i==0 || w==0)
K[i][w] = 0;
else if (P[i-1] <= w)
K[i][w] = max(V[i-1] + K[i-1][w-P[i-1]], K[i-1][w]);
else
K[i][w] = K[i-1][w];
}
}
return K[N][W];
}
int main()
{
int N,W,i;// N: Quantidade de Objetos - W: Capacidade da Mochila; i: interação
int Val=1;//V: Valor;
int Pes=1;//P: Peso;
do{
scanf("%d %d",&N,&W);//ler N e W
for (i=1;i<=N;i++) // iteração
scanf("%d %d",&Val,&Pes);//ler V
//ler P
int V[]={Val};//declaração do vetor V e recebendo Val do scanf
int P[]={Pes};//declaração do vetor P e recebendo Pes do scanf
printf("%d",knapsack(W, P, V, N));
printf("\n");
}while(N!=0 && W!=0);
return 0;
}
I need to enter the number of items N and the capacity W:
When I enter N = 1, W - 7 and the objects P = 4, V = 5 the output is 4.
If I enter other values such as N = 10, W = 25 and P = 3 3 3 3 3 3 3 3 3 3, V = 5 5 5 5 5 5 5 5 5 5, I receive 2005985278 instead of 15.
Please what's the error in my code?
Now my code is this but I receive the erro in my output:
3 10
7 6
5 5
4 5
1 7
4 5
the correct output is : 9 and 4 and i received 7 and 0;
in this case how may i add a end the programm when enter N==0 && W==0?
#include<stdio.h>
#include<stdlib.h>
#define MA 29
int max(int a, int b) {
return (a > b)? a : b;
}
int knapsack(int W, int P[], int V[], int N)
{
int i, w;//interação;
int K[N+1][W+1];//declaração de K recebendo o valor de N e W +1;
for (i = 0; i <=N; i++) // para i=0 i< = N incrementa i;
{
for (w = 0; w <= W; w++)
{
if (i==0 || w==0)
K[i][w] = 0;
else if (P[i-1] <= w)
K[i][w] = max(V[i-1] + K[i-1][w-P[i-1]], K[i-1][w]);
else
K[i][w] = K[i-1][w];
}
}
return K[N][W];
}
int main()
{
int N,W,i;// N: Quantidade de Objetos - W: Capacidade da Mochila; i: interação
//P: Peso;
while (scanf("%d %d", &N, &W) == 2)
{
int V[N];
int P[N];
for (i = 1; i <= N; i++)
if (scanf("%d %d", &V[i], &P[i]) != 2)
break;
printf("%d\n", knapsack(W, P, V, N));
}
}

Answer 1

Your problem is that you are allocating arrays of size 1 and then trying to access 10 elements in those arrays. C won't stop you trying, but it will usually give you the wrong answer.
Existing code:
do{
scanf("%d %d",&N,&W); // Should test for success and terminate loop on failure
for (i=1;i<=N;i++)
scanf("%d %d",&Val,&Pes); // Should check for success; should store values
int V[]={Val}; // V is an array with one entry, the last value entered as Val.
int P[]={Pes}; // P is an array with one entry, the last value entered as Pes.
printf("%d",knapsack(W, P, V, N));
printf("\n");
} while (N!=0 && W!=0);
C99 code:
while (scanf("%d %d", &N, &W) == 2)
{
int V[N];
int P[N];
for (i = 1; i <= N; i++)
if (scanf("%d %d", &V[i], &P[i]) != 2)
break;
printf("%d\n", knapsack(W, P, V, N));
}
Note that if you'd printed the inputs to your knapsack() function, either in the calling code or in the function itself, you'd have seen the trouble very quickly. It is a powerful technique to print your input data after you've finished reading it. Note that printing it while you're reading can mask problems that printing after you've finished reading will reveal.
Clearly, if your knapsack algorithm is incorrect, you'll still get wrong answers; I've not reviewed that and have no particular plans to do so. However, you should be getting the correct input data, which improves enormously the chances of getting the right output.