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Fernando Javier León
Asked: 2022-09-05 13:17:38 +0800 CST 2022-09-05 13:17:38 +0800 CST

How to add strings to an array in C

  • 772

I want to input strings to an array in C, the code I have is this:

int main()
{
    
    int sizeA;
    printf("Tamanio de arreglo\n");
    
    scanf("%i", &sizeA);
    
    char names[sizeA];
    
    
    for(int i = 0; i < sizeA; i++){
        printf("Nombre %c\n", i+1 );
        scanf("%c", &names[i]);
    }
    

    
    printf("valores arreglo\n");
    
    for(int i = 0; i < sizeA; i++){
        printf("%c", names[i]);
    }



    return 0;
    
}

First of all I ask the size of the array, in case of entering 5as the length of the array, when I enter the value of the strings at the time of requesting the Nombrename, I get the name request twice, which in the end allows me to enter 2the string only times and not the 5ones you enter as length. How can I enter the 5 values? Thanks in advance. When I do it with integers it lets me enter the 5 values ​​correctly and with strings it doesn't.

c

1 Answers

  1. Best Answer

    Several things to keep in mind:

    • In C, the size of arrays must be constant. The compiler should refuse to compile.

      To solve the first problem, you must resort to dynamic memory if you need variable-length arrays.

      You can allocate and free memory with mallocand freerespectively. For example:

      int size = 0;
scanf("%i", &size);
// Reservas memoria
// malloc recibe el número de bytes a reservar como parámetro 
int* arr = malloc(size * sizeof(int));
for (int i = 0; i < size; i++){
    scanf("%i", &arr[i]);
}
// Liberas la memoria al terminar de usarla
free(arr);

    • It is preferable to use scanfonly to read numbers or Boolean values. For characters or strings (no need to read or write characters individually), getcharand gets_sare better options.

    • When reading numbers, scanfit drops the line break similar to how it does in C++.

      In C you can discard the character with getchar(equivalent to fgetc(stdin)). In C++ you can do it with std::cin.ignore().

    • A string is an array of characters ( char*or char[]). If you want an array of strings, it would be char[][], char*[], char[]*or char**(the more you work with dynamic memory, the more likely you are to use the latter).

      Some examples:

      // Arreglo de nombres de 10 caracteres (9 sin el caracter nulo)
char nombres[][10] = { "Juan", "Pablo", "Tobías" };

// Arreglo de 5 nombres de 10 caracteres (9 sin el caracter nulo)
char nombres[5][10] = { "Juan", "Pablo", "Tobías" };

// Arreglo de nombres (como punteros) sin límite de tamaño
char *nombres[] = { "Juan", "Pablo", "Tobías" };

    With all the fixes, you would get code like this:

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

#define STRING_SIZE 10

int main()
{
    int sizeA;
    printf("Tamaño de arreglo:\n");
    
    scanf("%i", &sizeA);
    // Quita el salto de línea que scanf deja en stdin al leer números.
    getchar();
    
    // Reservas memoria para cada puntero
    char** names = malloc(sizeA * sizeof(char*));
    
    for(int i = 0; i < sizeA; i++){
        // Reservas memoria para cada nombre
        names[i] = malloc(STRING_SIZE * sizeof(char));
        printf("Nombre %i:\n", i+1);
        gets_s(names[i], STRING_SIZE);
    }
    
    printf("\nNombres:\n");
    
    for(int i = 0; i < sizeA; i++){
        printf("%i: %s\n", i + 1, names[i]);
    }

    return 0;
    
}

    You can try it here .

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