6.16.3 使用嵌套循环，按下面格式打印字母：

F

FE

FED

FEDC

FEDCB

FEDCBA

#include <stdio.h>

int main()
{
    const int ROWS = 6;

    for (int row(0); row != ROWS; ++row)
    {
        for (char ch('F'); ch >= 'F' - row; --ch)
            printf("%c",ch);

        printf("\n");
    }

    return 0;
}

 

6.16.4 使用嵌套循环，按下面格式打印字母：

A

BC

DEF

GHIJ

KLMNO

PQRSTU

#include <stdio.h>

int main()
{
    const int ROWS = 6;
    const int COLS = 6;
    char ch = 'A';
    
    for (int row(0); row != ROWS; ++row)
    {
        for (int col(0); col <= row; ++col, ++ch)
            printf("%c", ch);

        printf("\n");
    }

    return 0;
}

 

6.16.5

#include <stdio.h>

int main()
{
    printf("Input a letter: ");
    
    char ch;
    while (1 == scanf("%c", &ch))
    {
        if ('\n' == ch || ' ' == ch || '\t' == ch)
            continue;

        if (ch < 'A' || ch > 'z')
            printf("\nIt's not a letter, try again: ");
        else
            break;
    }

    if (ch >= 'a') ch -= 'a' - 'A';

    const int ROWS = ch - 'A' + 1;
    const char *SPACE = " ";

    for (int row(0); row != ROWS; ++row)
    {
        for (int col(0); col != ROWS - row; ++col)
            printf(SPACE);

        char chTmp = 'A';
        for (; chTmp != 'A' + row; ++chTmp)
            printf("%c", chTmp);

        for (; chTmp != 'A' - 1; --chTmp)
            printf("%c", chTmp);

        printf("\n");
    }

    return 0;
}