赵史元

1:#include<stdio.h>
int main()
{
int arr1[] = { 1, 2, 3 }, arr2[] = { 4, 5, 6 }, i, t;
printf(“arr1=”);
for (i = 0; i < 3; i++)
{
printf("%d “, arr1[i]);
}
printf(”\n");
printf(“arr2=”);
for (i = 0; i < 3; i++)
{
printf("%d “, arr2[i]);
}
printf(”\n");
for (i = 0; i < 3; i++)
{
t = arr1[i];
arr1[i] = arr2[i];
arr2[i] = t;
}
printf(“new arr1=”);
for (i = 0; i < 3; i++)
{
printf("%d “, arr1[i]);
}
printf(”\n");
printf(“new arr2=”);
for (i = 0; i < 3; i++)
{
printf("%d “, arr2[i]);
}
printf(”\n");
system(“pause”);
return 0;
}
2：#include <stdio.h>
void main()
{
int i;
float a = 1, sum = 0;
for (i = 1; i < 101; i++)
{
sum = sum + a / i;
a = a * (-1);
}
printf(“1-1/2+1/3-1/4…-1/100=%f\n”, sum);
system(“pause”);
}
3：
#include <stdio.h>
int main(void)
{
int n = 1;
int count = 0;
while (n < 100)
{
if (n % 10 == 9) count++;
if (n % 100 - n % 10 == 90) count++;
n++;
}
printf(“9出现的次数：%d\n”, count);
system(“pause”);
return 0;
}