哈哈。希望我们都能突飞猛进

抱歉，你说的三角形我不会，直角三角形就会点。你看看吧
#include <stdio.h>
int main()
{
    //最简单的方法，别见怪。嘿嘿
    printf("                A\n");
    printf("               BAB\n");
    printf("              CBABC\n");
    printf("             DCBABCD\n");
    printf("            EDCBABCDE\n");
    //////////////////////////////////
    char ch[26]={'A','B','C','D','E','F','G','H',
                 'I','J','K','L','N','M','O','P','Q',
                 'R','S','T','U','V','W','X','Y','Z'
    };
    for (int x=0;x<20;x++)
    {  
        printf("%c",ch[x]);
        for (int y=0;y<x;y++)
        {
            printf("%c",ch[x]);
            printf("%c",ch[y]);
        }
        printf("\n");
    }
    return 0;
}