Create a recursive function in C that returns the largest and smallest value of a vector

Question

Guys, how can I solve this exercise?

1-on the first line the user has to type the vector size 2- in the second line, the user fills in integers 3- make a recursive function that receives by reference the variables of higher and lower values. The vector should be dynamically allocated.

I’m picking up a lot on this dynamic allocation. I did a sketch down here and I’m more lost than blind in a gunfight -.-

void procurar(int vetor[], int *tamanho, int *maior, int *menor){    

int i, j, aux; 

  for(i = 1; i < *tamanho; i++){ 
    j = i; 

    while((j != 0) && (*vetor[j] > *vetor[j - 1])) { 
      aux = *vetor[j]; 
      *vetor[j] = *vetor[j - 1]; 
      *vetor[j-1] = aux; 
      j--;     
    } 
  }

  *maior = *vetor[*tamanho];
  *menor = *vetor[0];
}



int main(){

    int tamanho, i, maior, menor;

    maior = 0;

    scanf("%d", &tamanho);

    int vetor[tamanho];

    for(i=0; i<tamanho; i++){
        scanf("%d", &vetor[i]);
    }

    procurar(&vetor, &tamanho, &maior, &menor);


    printf("%d %d", maior, menor);``

    return 0;
}

Answer 1

I don’t know from which version of the C pattern one can allocate an array on the stack, as you did, using a variable as size index; or it’s C99 or C11. But if you want more C89-compatible code (which, for example, works with MSFT compilers), you’re better off using malloc():

#include <stdio.h>
#include <stdlib.h>

/* implementação de "procurar()" omitida */

int main() {
    int tamanho, i, maior, menor;
    int * vetor;

    if (scanf("%d", &tamanho) < 1 || tamanho < 1) {
        fputs("Não consegui ler o tamanho do vetor\n", stderr);
        return EXIT_FAILURE;
    }
    vetor = malloc(tamanho * sizeof (int));
    if (vetor == NULL) {
        fputs("Não consegui alocar o vetor\n", stderr);
        return EXIT_FAILURE;
    }

    for (i = 0; i < tamanho; i ++) {
        if (scanf("%d", &vetor[i]) < 1) {
            fprintf(stderr, "Não consegui ler o %dº valor do vetor\n", i + 1);
            return EXIT_FAILURE;
        }
    }

    procurar(vetor, tamanho, &maior, &menor);
    fprintf("O maior número é %d e o menor, %d\n", maior, menor);

    return EXIT_SUCCESS;
}

As to the procurar() proper, it is good to remember that recursion is an implementation of the mathematical technique of induction, so you have to define a base case and a inductive step. As you are dealing with vectors, a good variable to induce is the size of the vector; then, in this case, the base case is when you have a vector of length 1 and the inductive step is the result of the function on a subvector of the current vector (for example, the vector starting from the second element). As a kid:

void procurar(int vetor[], int tamanho, int * maior, int * menor) {
    if (tamanho == 1) { /* caso base */
        * maior = * menor = vetor[0];
    } else { /* passo indutivo */
        procurar(vetor + 1, tamanho - 1, maior, menor);
        if (vetor[0] > * maior) * maior = vetor[0];
        if (vetor[0] < * menor) * menor = vetor[0];
    }
}