Put random value from array in other array letter by letter - c

Question

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
void initRandom() {
srand(time(NULL));
}
int intUniformRnd(int a, int b){
return a + rand() % (b-a+1);
}
const char* animaisQuatro[] = {"gato", "urso","vaca"};
int main() {
char quatro[4] = {'*' , '*' , '*', '*'};
initRandom();
printf("%s\n", animaisQuatro[intUniformRnd(0,2)]);
for(int i=0;i<4;i++){
printf("%c", quatro[i]);
}
return 0;
}
I have this code that give me a random animal from the array const char* animaisQuatro[] = {"gato", "urso","vaca","lapa"}; from here
initRandom();
printf("%s\n", animaisQuatro[intUniformRnd(0,2)]);
and then I want to put that random animal in another array letter by letter but I don't know how

Answer 1

First I reduced your code to a minimal and reproducible example (something you should do whenever you ask a question):
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
void initRandom() {
srand(time(NULL));
}
int intUniformRnd(int a, int b){
return a + rand() % (b-a+1);
}
const char* animaisQuatro[] = {"gato", "urso","vaca"};
int main() {
char quatro[4] = {'*' , '*' , '*', '*'};
initRandom();
printf("%s\n", animaisQuatro[intUniformRnd(0,2)]);
for(int i=0;i<4;i++){
printf("%c", quatro[i]);
}
return 0;
}
Then you can proceed like this:
int main() {
char quatro[4] = {'*' , '*' , '*', '*'};
initRandom();
// Get the animal name from a random position
char* name = animaisQuatro[intUniformRnd(0, 2)];
// Iterate four times
for (int i = 0; i < 4; i++) {
// Assign each `name` index to its respective `quatro` position
quatro[i] = name[i];
}
printf("%s", quatro);
return 0;
}
Tip: you can avoiding hardcoding the 2 when calling intUniformRnd. Note that
printf("%d\n", (int) sizeof(animaisQuatro));
printf("%d\n", (int) sizeof(char*));
printf("%d\n", (int) sizeof(animaisQuatro) / sizeof(char*));
outputs
24
8
3
Therefore, you can do
int length = (int) sizeof(animaisQuatro) / sizeof(char*);
int pos = intUniformRnd(0, length - 1);
This way, if you want to add more elements to animaisQuatro, you don't need to change the value inside intUniformRnd.

Answer 2

I want to put that random animal in other array letter by letter
To copy a string to another character array, code could use
// Risky
strcpy(quatro, animaisQuatro[intUniformRnd(0,2)]);
That would overflow quatro[] if it is too small and leads to undefined behavior. (Bad)
A better way to copy and prevent buffer overflow and alert of a failure:
int len = snprintf(quatro, sizeof quatro, "%s", animaisQuatro[intUniformRnd(0,2)]);
if (len >= sizeof quatro) {
fprintf(stderr, "quatro too small.\n");
}
Since C99 and selectively afterword, code could use a variable length array to form a right-size quatro array.
const char *animal = animaisQuatro[intUniformRnd(0,2)];
size_t sz = strlen(animal) + 1;
char quatro[sz];
strcpy(quatro, animal);
Yet since intUniformRnd[] is constant, no need to copy the text, just copy the address to a pointer:
const char *quatro = animaisQuatro[intUniformRnd(0,2)];