1.输出100-200内的素数，并输出个数
#include <stdio.h>
int main()
{
int i;
int j;
int flag = 0;
int count = 0;
for(i = 100; i <= 200; i++)
{
for(j = 2; j <= i / 2; j++)
{
if(i % j == 0)
{
flag = 1;
break;
}
}
if(flag != 1)
{
count++;
printf("%d\t",i);
}
flag = 0;
}
printf("\n");
printf("number:%d\n",count);
return 0;
}
2.输出1~1000内的完数
#include <stdio.h>
int main()
{
int i;
int j;
int sum = 0;
for(i = 1;i <= 1000; i++)
{
for(j = 1; j <= i / 2; j++)
{
if(i % j == 0)
{
sum = sum + j;
}
}
if(sum == i)
{
printf("%d\n",i);
}
sum = 0;
}
return 0;
}
3.1至某个数，这些数中出现9的次数
#include <stdio.h>
int main()
{
int i;
int num;
int temp;
int count = 0;
printf("please input number:");
scanf("%d",&num);
for(i = 1; i<= num; i++)
{
temp = i;
while(temp != 0)
{
if(temp % 10 == 9)
{
count = count + 1;
}
temp = temp / 10;
}
}
printf("number is : %d\n",count);
return 0;
}
4.输入三个数，输出最大的数
#include <stdio.h>
int main()
{
int a;
int b;
int c;
printf("please input three number:\n");
scanf("%d%d%d",&a,&b,&c);
if(a <= b)
{
a = b;
if(a <= c)
{
a = c;
}
}
else
{
if(a <= c)
{
a = c;
}
}
printf("max = :%d\n",a);
return 0;
}
5.判断一个数能否同时被3和5整除
#include <stdio.h>
int main()
{
int n;
printf("please input number:\n");
scanf("%d",&n);
if(n % 3 == 0 && n % 5 == 0)
{
printf("sucess!\n");
}
else
{
printf("can't\n");
}
}
6.用数组倒序输出0-9
#include <stdio.h>
int main()
{
int i;
int a[10];
for(i = 0; i <= 9; i++)
{
a[i] = i;
}
for(i = 9; i >= 0; i--)
{
printf("%d",a[i]);
}
printf("\n");
return 0;
}
7.求Fibonacci数列
#include <stdio.h>
int main()
{
int i;
int a[30] = {1,1};
for(i = 2; i <= 30; i++)
{
a[i] = a[i - 1] + a[i - 2];
}
for(i = 0;i <= 30; i++)
{
if(i % 6 == 0)
{
printf("\n");
}
printf("d",a[i]);
}
printf("\n");
return 0;
}
8.输入一个二维数组，输出它的转置
#include <stdio.h>
int main()
{
int i;
int j;
int a[2][3];
int b[3][2];
printf("please input 2d :\n");
for(i = 0;i <= 1; i++)
{
for(j = 0; j <= 2; j++)
{
scanf("%d",&a[i][j]);
}
}
printf("array a:\n");
for(i = 0;i <= 1; i++)
{
for(j = 0; j <= 2; j++)
{
printf("=",a[i][j]);
b[j][i] = a[i][j];
}
printf("\n");
}
printf("array b:\n");
for(i = 0; i <= 2; i++)
{
for(j = 0; j <= 1; j++)
{
printf("=",b[i][j]);
}
printf("\n");
}
return 0;
}
9.输入字符串，输出整数
#include <stdio.h>
#include <string.h>
#include <math.h>
#define MAX_SIZE 10
int main()
{
int i;
int j;
int len;
int num = 0;
char str[MAX_SIZE];
printf("please input string:\n");
gets(str);
len = strlen(str);
for(i = 0; i <= len - 1; i++)
{
j = str[i] - '0';
num = num * 10 + j;
}
printf("number is :%d\n",num);
return 0;
}
10.输入整数，输出字符串
#include <stdio.h>
#include <string.h>
#include <math.h>
#define MAX_SIZE 10
int main()
{
int i;
int j;
int len;
int num = 0;
char str[MAX_SIZE];
printf("please input string:\n");
gets(str);
len = strlen(str);
for(i = 0; i <= len - 1; i++)
{
j = str[i] - '0';
num = num * 10 + j;
}
printf("number is :%d\n",num);
return 0;
}
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