loop c

#include <stdio.h>

int main(int argc, char const *argv[])
{
    /* 1 */
    for (int i = 0; i < 10; ++i)
        printf("* ");
    printf("\n\n");

    /* 2 */
    for (int i = 0; i < 10; ++i)
        printf("* ");
    printf("\n");

    for (int i = 0; i < 5; ++i)
        printf("* ");
    printf("\n");

    for (int i = 0; i < 15; ++i)
        printf("* ");
    printf("\n\n");

    /* 3 */
    for (int i = 0; i < 10; ++i){
        for (int j = 0; j < 10; ++j)
            printf("* ");
        printf("\n");
    }
    printf("\n");

    /* 4 */
    for (int i = 0; i < 10; ++i){
        for (int j = 0; j < 5; ++j)
            printf("* ");
        printf("\n");
    }
    printf("\n");

    /* 5 */
    for (int i = 0; i < 5; ++i){
        for (int j = 0; j < 20; ++j)
            printf("* ");
        printf("\n");
    }
    printf("\n");

    /* 6 */
    for (int i = 0; i < 10; ++i){
        for (int j = 0; j < 10; ++j)
            printf("%d ", j);
        printf("\n");
    }
    printf("\n");

    /* 7 */
    for (int i = 0; i < 10; ++i){
        for (int j = 0; j < 10; ++j)
            printf("%d ", i);
        printf("\n");
    }
    printf("\n");

    /* 8 */
    for (int i = 0; i < 10; ++i){
        for (int j = 0; j < i+1; ++j)
            printf("%d ", j);
        printf("\n");
    }
    printf("\n");

    /* 9 */
    for (int i = 0; i < 10; ++i){
        for (int j = 0; j < i; ++j)
            printf("  ");
        for (int j = 0; j < 10-i; ++j)
            printf("%d ", j);
        printf("\n");
    }
    printf("\n");

    /* 10 */
    for (int i = 1; i < 10; ++i){
        for (int j = 1; j < 10; ++j){
            if (i*j < 10)
                printf(" ");
            printf("%d ", i * j);
        }
        printf("\n");
    }
    printf("\n");

    /* 11 */
    for (int i = 0; i < 10; ++i) {
        for (int j = 0; j < 10-i; ++j)
            printf("  ");
        for (int j = 1; j < i+1; ++j)
            printf("%d ", j);
        for (int j = i-1; j > 0; --j)
            printf("%d ", j);
        printf("\n");
    }
    printf("\n");

    /* 12 */
    for (int i = 0; i < 10; ++i){
        for (int j = 0; j < 10-i; ++j)
            printf("  ");
        for (int j = 1; j < i+1; ++j)
            printf("%d ", j);
        for (int j = i-1; j > 0; --j)
            printf("%d ", j);
        printf("\n");
    }

    for (int i = 0; i < 10; ++i){
        for (int j = 0; j < i+2; ++j)
            printf("  ");
        for (int j = 1; j < 9-i; ++j)
            printf("%d ", j);
        printf("\n");
    }
    printf("\n");

    /* 13 */
    for (int i = 0; i < 10; ++i){
        for (int j = 0; j < 10-i; ++j)
            printf("  ");
        for (int j = 1; j < i+1; ++j)
            printf("%d ", j);
        for (int j = i-1; j > 0; --j)
            printf("%d ", j);
        printf("\n");
    }

    for (int i = 0; i < 10; ++i){
        for (int j = 0; j < i+2; ++j)
            printf("  ");
        for (int j = 1; j < 9-i; ++j)
            printf("%d ", j);
        for (int j = 7-i; j > 0; --j)
            printf("%d ", j);
        printf("\n");
    }

    return 0;
}