Basic programming questions

sym-tri.c

/**
 * Question: https://www.zhihu.com/question/55234202
 * Usage: <proc> <lines>
 * Example: ./a.out 6
 *      A
 *     ABA
 *    ABCBA
 *   ABCDCBA
 *  ABCDEDCBA
 * ABCDEFEDCBA
 */
#include <stdio.h>
#include <stdlib.h>

void print(int lines)
{
    int blanks = lines - 1;
    char ch = 'A';

    for (int line = 0; line < lines; line++) {
        for (int i = 0; i < blanks; i++) {
            putchar(' ');
        }
        for (int i = 0; i <= line; i++) {
            putchar(ch + i);
        }
        for (int i = line - 1; i >= 0; i--) {
            putchar(ch + i);
        }
        putchar('\n');
        blanks--;
    }
}

int main(int argc, char *argv[])
{
    print(atoi(argv[1]));
}