Why don’t you get in the loop?

Question

I’m storing student names and grades and trying to display name, grades and media. The problem is that the program is skipping the loop of notes and is only taking the name.

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

/*
Síntese
Objetivo: Calcular a média das notas de um aluno
Entrada: Nome, Nota 1, nota 2, nota 3, e nota 4
Saída: Nome, notas do aluno e média
*/


#define MAX_NOME 100
#define MAX_NOTAS 4
#define VETOR_MAX 50
typedef struct Alunos{
    char nome[MAX_NOME];
    int notas[MAX_NOTAS];
}Aluno;

int leValidaOpcao();
int main(int argc, char *argv[]) {
    int cont=0, cont2=0, qtdAlunos=0, soma;
    char continuar = ' ';
    float media=0.0;

    Aluno * aluno1 = malloc(qtdAlunos * sizeof(Aluno));


    do{
        printf("Informe o %d%c nome :", cont+1, 167);
        scanf(" %[^\n]s", (aluno1+cont)->nome);

        for(cont2; cont2 < MAX_NOTAS;cont2++){
            printf("Informe a nota %d:", cont2+1);
            scanf("%d", &(aluno1+cont)->notas[cont2]);
            soma += (aluno1+cont)-> notas[cont2];
            system("cls");
        }

        printf("Nome = %s\n", (aluno1+cont)->nome);
        for(cont2; cont2 < MAX_NOTAS; cont2++){
            printf("Nota[%d] =  %d\n", cont2+1, (aluno1+cont)->notas[cont2]);
        }
        printf("\nMedia = %f", soma/MAX_NOTAS);

        continuar = leValidaOpcao();
        cont++;
    }while(continuar == 's' && cont < VETOR_MAX);


    free(aluno1);
    return 0;
}
int leValidaOpcao(){
    char opcao = ' ';
    int flag = 1;


    do{
        printf("Deseja continuar (S - sim ou Nao - N)");
        scanf(" %c", &opcao);
        opcao = tolower(opcao);

        if(opcao != 's' && opcao != 'n'){
            printf("\nOpcao invalida!\n");
            flag = 0;
        }
    }while(!flag);
    return opcao;
}

Answer 1

The problem is using the same variable cont2 in both loops.

    for(cont2; cont2 < MAX_NOTAS;cont2++){
        printf("Informe a nota %d:", cont2+1);
        scanf("%d", &(aluno1+cont)->notas[cont2]);
        soma += (aluno1+cont)-> notas[cont2];
        system("cls");
    }

    printf("Nome = %s\n", (aluno1+cont)->nome);

    for(cont2; cont2 < MAX_NOTAS; cont2++){
        printf("Nota[%d] =  %d\n", cont2+1, (aluno1+cont)->notas[cont2]);
    }
    printf("\nMedia = %f", soma/MAX_NOTAS);

Because you initialize do not assign the value 0 to the variable after the first loop, it will start the second loop with the end value of the first loop, ie MAX_NOTAS - 1.

To solve this problem, you can use different variables in each loop or initialize the variable cont2 again, for example:

for(cont2; cont2 < MAX_NOTAS;cont2++){
    printf("Informe a nota %d:", cont2+1);
    scanf("%d", &(aluno1+cont)->notas[cont2]);
    soma += (aluno1+cont)-> notas[cont2];
    system("cls");
}

printf("Nome = %s\n", (aluno1+cont)->nome);

cont2 = 0;

for(cont2; cont2 < MAX_NOTAS; cont2++){
    printf("Nota[%d] =  %d\n", cont2+1, (aluno1+cont)->notas[cont2]);
}
printf("\nMedia = %f", soma/MAX_NOTAS);