Output 数组作为“字符串”，在 c 中用逗号分隔

Question

I have the following array:

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

int main () {

int openedLockers[5] = {0,1,2,3,4};


return 0;
}

And would like to output "Opened Lockers: 0,1,2,3,4."

It specifically has to end with a period after the last number. I'm not sure how to do this in a for loop in a way that I do not have to print the "Opened Lockers: " part more than once.

Answer 1

#include <stdio.h>

int main () {

int openedLockers[] = {0,1,2,3,4};

printf("Opened Lockers: ");

for (size_t i = 0; i < 5; i++) {
    printf("%d", openedLockers[i]);

    if (i != 4)
        printf(",");
    else
        printf(".");
}
return 0;
}


// Output : Opened Lockers: 0,1,2,3,4.

Answer 2

A super easy way to achieve the desired format is to use a conditional (ternary) operator as part of your printf format string within the output loop, eg

#include <stdio.h>

int main (void) {

    int openedLockers[] = {0,1,2,3,4},
        n = sizeof openedLockers / sizeof *openedLockers;

    fputs ("Opened Lockers: ", stdout);

    for (int i = 0; i < n; i++)
        printf (i ? ",%d" : "%d", openedLockers[i]);
    puts (".");

    return 0;
}

Example Use/Output

$ ./bin/openlockers
Opened Lockers: 0,1,2,3,4.

Look things over and let me know if you have further questions.

Answer 3

To do that without branches:

#include <stddef.h>
#include <stdio.h>

int main (void)
{
    int openedLockers[] = {0, 1, 2, 3, 4};
    size_t const n = sizeof openedLockers / sizeof *openedLockers;

    printf("Opened Lockers: ");

    for (size_t i = 0; i < n; ++i)
        printf("%d,", openedLockers[i]);

    puts("\b."); // overwrite the last comma with a period and add a newline.
}

Answer 4

#include <stddef.h>
#include <stdio.h>

int main (void)
{
    int openedLockers[] = {0, 1, 2, 3, 4};
    int const n = sizeof openedLockers / sizeof *openedLockers;

    printf("Opened Lockers: ");

    for (int i = 0; i < n; ++i)
        printf("%d,", openedLockers[i]);

    printf("\b.");
}

Answer 5

Loop only the repeated part to avoid if s or other conditional constructs. Note that the repeated part repeats one less time than the number of elements.

// before repeats, include first element
printf("Opened Lockers: %d", openedLockers[0]);

// repeat comma, space, element
for (int i = 1; i < 5; i++) {
    printf(", %d", openedLockers[i]);
}

// after repeats
printf(".\n");

Answer 6

#include <stdio.h>

void print_array(int *a, int n);
int main(void)
{
    int array[5];

    array[0] = 98;
    array[1] = 402;
    array[2] = -198;
    array[3] = 298;
    array[4] = -1024;
    print_array(array, 5);
    return 0;
}
void print_array(int *a, int n){
    int i = 0;
    for (i = 0; i <= n - 1; i++){
        printf("%d ,",a[i]);
    }
}