回顾习题1

 

读取键盘输入字符的数目：

test1.c

#include <stdio.h>
int main(){
        int num=0;
        char c;
        while ( (c=getchar()) != '\n'){
                num++;
                                        }
        printf("Enter number is :%d\n",num);
}

test2.c

#include <stdio.h>
int main()
{
        int num=0;
        char c;
loop:
        if ( (c=getchar() ) != '\n' )
        {
                num ++;
                goto loop;
        }
        printf("Enter number is :%d\n",num);
}

输出101-200之间的所有素数。注：用这个数分别除 2到这个数加1的平方根 范围内

的每个数。

sushu.c

#include <stdio.h>
#include <math.h>
int main()
{
        int num,i;
        float sqr;
        for (num = 101;num <= 200;num++)
        {
                sqr=sqrt(num+1);
                for (i=2;i<sqr;i++)
                {
                        if ( (num/i)!=0 )
                                printf("%d  ",num);
                }
        }
}

编译错误，错误代码：
/tmp/ccc4UFlw.o(.text+0x1b): In function `main':
: undefined reference to `sqrt'
collect2: ld returned 1 exit status
Q:以上意思好像是说找不到sqrt函数，问题在哪？

打印九九乘法表：

chengfa1.c

#include <stdio.h>
int main()
{
        int j,k;
        for (j=1;j<=9;j++)
        {
                for (k=1;k<=j;k++)
                {
                        printf("%4d",j*k);
                }
         printf("\n");
        }
}

chengfa2.c

#include <stdio.h>
int main()
{
        int a[9][9];
        int j,k;
        for (j=1;j<=9;j++)
        {
                for (k=1;k<=j;k++)
                {
                        a[j-1][k-1]=j*k;
                        printf("%4d",a[j-1][k-1]);
                }
                printf("\n");
        }
}