Save mutliple strings of variable length in a single array in C

Question

I'm trying to make a QnA game that will take 5 random questions from a pool of 10 and print them to let the user answer. I have a 2D array to save 10 strings that will be the questions. My work so far:

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

void qna(){
    int i;
    
    char er[10][13]; //10 questions
    
    er[0][]="2+2"; //ans 4
    er[1][]="4-5"; //ans -1
    er[2][]="10*10"; //ans 100
    er[3][]="17*3"; //ans 51
    er[4][]="9/3"; //ans 3
    er[5][]="45+24+35-68"; //ans 36
    er[6][]="4-2"; //ans 2
    er[7][]="592-591"; //ans 1
    er[8][]="8+3"; //ans 11
    er[9][]="9*9"; //answer 81
    
    for(i = 0; i < 10; i++){ //test to see if strings save correctly
        printf("%s\n", er[i]);
    }
    
}

int main() 
{
    qna();
    return 0;
    
}

When I compile the program, I get an error "[Error] expected expression before ']' token" for every line that assigns a string to er. Then I tried this:

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

void qna(){
    int i;
    
    char er[10][13]; //10 questions
    
    er[0][13]="2+2"; //ans 4
    er[1][13]="4-5"; //ans -1
    er[2][13]="10*10"; //ans 100
    er[3][13]="17*3"; //ans 51
    er[4][13]="9/3"; //ans 3
    er[5][13]="45+24+35-68"; //ans 36
    er[6][13]="4-2"; //ans 2
    er[7][13]="592-591"; //ans 1
    er[8][13]="8+3"; //ans 11
    er[9][13]="9*9"; //answer 81
    
    for(i = 0; i < 10; i++){ //test to see if strings save correctly
        printf("%s\n", er[i]);
    }
    
}

int main() 
{
    qna();
    return 0;
    
}

When I run this I get a warning "[Warning] assignment makes integer from pointer without a cast" instead of an error on the same lines as before. The command line window prints weird symbols instead of the strings, and some lines are blank entirely. How do I fix this?

Go back to your textbook where you learned to copy strings via strcpy. — Cheatah
– Cheatah, Commented Nov 5, 2022 at 13:47
When you assign a string. You don't copy it, you assign the pointer to a string stored somwhere else. Declaring a string in "" makes the conpiler store it in constant memory. So you don't need to define the size of them. Just use an array of 10 pointer to chars. They will all point to different locations. You never need the value 13 — user2302957
– user2302957, Commented Nov 5, 2022 at 13:49

user16004728 · Accepted Answer · 2022-11-05 13:53:08Z

2

Since you don't seem to be changing the contents of any of these strings, you can use an array of pointers to (read-only) strings in memory:

char* er[] = {
    "2+2", //ans 4
    "4-5", //ans -1
    "10*10", //ans 100
    "17*3", //ans 51
    "9/3", //ans 3
    "45+24+35-68", //ans 36
    "4-2", //ans 2
    "592-591", //ans 1
    "8+3", //ans 11
    "9*9" //answer 81
};

answered Nov 5, 2022 at 13:53

user16004728

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user20341797 · Accepted Answer · 2022-11-05 13:54:52Z

0

Use strcpy to copy the strings into the buffer.

strcpy(er[0], "2+2");
strcpy(er[1], "4-5");
//etc.

or just initialize at creation:

char er[10][13] = {
   "2+2",
   //...
};

answered Nov 5, 2022 at 13:54

user20341797

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