第 6 章 C控制语句：循环

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 = ;

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

         printf("\n");
     }

     return ;
 }

6.16.3

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 = ;
     const int COLS = ;
     char ch = 'A';

     for (int row(); row != ROWS; ++row)
     {
         for (int col(); col <= row; ++col, ++ch)
             printf("%c", ch);

         printf("\n");
     }

     return ;
 }

6.16.4

6.16.5

 #include <stdio.h>

 int main()
 {
     printf("Input a letter: ");

     char ch;
     while ( == 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' + ;
     const char *SPACE = " ";

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

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

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

         printf("\n");
     }

     return ;
 }

6.16.5