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：

FED

FEDC

FEDCB

FEDCBA

 1 #include <stdio.h>
 2 
 3 int main()
 4 {
 5     const int ROWS = 6;
 6 
 7     for (int row(0); row != ROWS; ++row)
 8     {
 9         for (char ch('F'); ch >= 'F' - row; --ch)
10             printf("%c",ch);
11 
12         printf("
");
13     }
14 
15     return 0;
16 }

6.16.3

6.16.4 使用嵌套循环，按下面格式打印字母：

DEF

GHIJ

KLMNO

PQRSTU

 1 #include <stdio.h>
 2 
 3 int main()
 4 {
 5     const int ROWS = 6;
 6     const int COLS = 6;
 7     char ch = 'A';
 8     
 9     for (int row(0); row != ROWS; ++row)
10     {
11         for (int col(0); col <= row; ++col, ++ch)
12             printf("%c", ch);
13 
14         printf("
");
15     }
16 
17     return 0;
18 }

6.16.4

6.16.5

 1 #include <stdio.h>
 2 
 3 int main()
 4 {
 5     printf("Input a letter: ");
 6     
 7     char ch;
 8     while (1 == scanf("%c", &ch))
 9     {
10         if ('
' == ch || ' ' == ch || '	' == ch)
11             continue;
12 
13         if (ch < 'A' || ch > 'z')
14             printf("
It's not a letter, try again: ");
15         else
16             break;
17     }
18 
19     if (ch >= 'a') ch -= 'a' - 'A';
20 
21     const int ROWS = ch - 'A' + 1;
22     const char *SPACE = " ";
23 
24     for (int row(0); row != ROWS; ++row)
25     {
26         for (int col(0); col != ROWS - row; ++col)
27             printf(SPACE);
28 
29         char chTmp = 'A';
30         for (; chTmp != 'A' + row; ++chTmp)
31             printf("%c", chTmp);
32 
33         for (; chTmp != 'A' - 1; --chTmp)
34             printf("%c", chTmp);
35 
36         printf("
");
37     }
38 
39     return 0;
40 }

6.16.5