Homework Number 8

#include <stdio.h>

int main(void)
{
int i, x;
char choice;
char str[100];

printf("\nPlease enter a string:\t");
gets(str);

printf("(e)ncrypt or (d)ecrypt?");
scanf("%c", &choice);

if (choice == 'e'){
for(i = 0; (i < 1000 && str[i] != '\0'); i++)
printf(" %i", str[i]+4);
if ((int)(str[i]+ 4) <= 122){
str[i] = str[i] + 4; }
if ((int)(str[i] + 4) > 122){
x = ((int)str[i] + 4 - 122);
str[i] = (char)(97 + x -1) ;
}


printf("\nEncrypted string: %s\n", str);
}

if (choice == 'd'){
for(i = 0; (i < 1000 && str[i] != '\0'); i++)
if ((str[i]- 4) >= 97){
str[i] = str[i] - 4; }
if ((str[i] - 4) < 97){
x = (97 - (int)str[i] + 4);
str[i] = (char)(122 - x +1);
}

printf("\nDecrypted string: %s\n", str);
}
}
RANDOM INTS
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#define n 10


double a, b;
double rand_float(double interval_start, double interval_end);
double r, average, sum, sum_list, variance, xn_minus_a;
int rand_floats[n];
float xn_minus_a_squared[n];

int main(void) {
srand(26);
for (int i =0; i<n; i++ ){
  r = rand_float(4, 10);
  printf(" %f \n", r);
  sum = sum +r;
  rand_floats[i] = r;
}
average = sum/n;
for (int i =0; i<n; i++){
  xn_minus_a= rand_floats[i] - average;
  xn_minus_a_squared[i] = (xn_minus_a)*(xn_minus_a);
}
for (int i = 0; i<n; i++){
  sum_list = sum_list + (xn_minus_a_squared[i]);
}
variance = sum_list/n-1;
printf(" variance = %f \n", variance);
printf(" average = %f \n", average);
}
double rand_float(double interval_start, double interval_end)
{
 
return ((rand() % 32767)/32767.0)*(interval_end-interval_start)+ interval_start;
}

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