PTA----- 数字加密 (15分)

#include<stdio.h>
int main()
{
int i = 3, x;
int a[4];
int temp;
scanf("%d", &x);
while (i != -1)
{
a[i] = x % 10;
x = x / 10;
i--;
}
for (i = 0; i < 4; i++)
{
a[i] = a[i] + 9;
}
for (i = 0; i < 4; i++)
{
a[i] = a[i] % 10;
}
for (i = 0; i < 2; i++)
{
temp = a[i];
a[i] = a[i + 2];
a[i + 2] = temp;
}
printf("The encrypted number is ");
for (i = 0; i < 4; i++)
{
printf("%d", a[i]);
}
return 0;
}