学点 C 语言(7): for 循环

1. for 循环的基本形式:

   include <stdio.h>

int main(void)
{

int i;
for (i = 0; i < 10; i++) {
    printf("%d\n", i);
}
getchar();
return 0;

}

2. 步长:

   include <stdio.h>

int main(void)
{

int i;
for (i = 0; i < 10; i += 2) {
    printf("%d\n", i);
}
getchar();
return 0;

}

3. 递减:

   include <stdio.h>

int main(void)
{

int i;
for (i = 10; i > 0; i--) {
    printf("%d\n", i);
}
getchar();
return 0;

}

4. 可用字符:

   include <stdio.h>

int main(void)
{

char c;

for (c = 'A'; c <= 'Z'; c++)
    printf("%c\n", c);

putchar('\n');

for (c = 'z'; c >= 'a'; c--)
    printf("%c\n", c);

getchar();
return 0;

}

5. 可用小数:

   include <stdio.h>

int main(void)
{

double f;
for (f = 0.0f; f < 2; f += 0.3) {
    printf("%.1f\n", f);
}
getchar();
return 0;

}

6. 携带其他变量:

   include <stdio.h>

int main(void)
{

int i, j=0;
for (i = 0; i < 10; i++, j = i*2) {
    printf("%d,%d\n", i,j);        
}
getchar();
return 0;

}

include <stdio.h>

int main(void)
{

int i, j=999;
for (i = 0; i < 10; j = i++) {
    printf("%d,%d\n", i,j);
}
getchar();
return 0;

}

7. 嵌套:

   include <stdio.h>

int main(void)
{

int i,j;
for (i = 0; i < 10; i++) {
    for (j = 0; j < 10; j++) {
        printf("%2d ", i*j);        
    }
    printf("\n");
}
getchar();
return 0;

}

8. break:

   include <stdio.h>

int main(void)
{

int i;
for (i = 0; i < 10; i++) {
    if (i == 5) break;
    printf("%d\n", i);
}
getchar();
return 0;

}

9. continue:

   include <stdio.h>

int main(void)
{

int i;
for (i = 0; i < 10; i++) {
    if (i%5 == 0) continue;
    printf("%d\n", i);
}
getchar();
return 0;

}

10. 省略:

    include <stdio.h>

int main(void)
{

int i=0;
for (; i < 10; i++) {
    printf("%d\n", i);
}
getchar();
return 0;

}

include <stdio.h>

int main(void)
{

int i;
for (i = 0; ; i++) {
    if (i > 10) break;
    printf("%d\n", i);
}
getchar();
return 0;

}

include <stdio.h>

int main(void)
{

int i;
for (i = 0; i < 10; ) {
    i++;
    printf("%d\n", i);
}
getchar();
return 0;

}

include <stdio.h>

int main(void)
{

int num = 0;
for (;;) {
    printf("%d\n", num);
    num++;
    if (num > 10) break;
}
getchar();
return 0;

}

11. 简化布尔判断

    include <stdio.h>

int main(void)
{

int i;
for (i = 10; i > 0; i--) printf("%d\n", i); /* 其中的 i > 0 是个布尔判断 */   
for (i = 10; i; i--) printf("%d\n", i);  /* 因为 i = 0 即为假, 也可省略; 这和上一句一样 */
getchar();
return 0;

}

12. 实例: 输出 0-100 的整数, 10 个一换行

    include <stdio.h>

int main(void)
{

int i;
for (i = 0; i < 100; i++) {
if((i%10 == 0) && i) putchar('\n');
    printf("%2d ", i);
}
getchar();
return 0;

}

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