Why does my program skip a switch instruction? - c

Question

I am trying to write a program, where after 7 floats inputted by the user; they get stored into an array, then get printed out like this:
DAY VALUE ISTOGRAM
1 37.8 ***
2 40.6 ******
where the number of * in the Istogram column is given by value - 34.
I've written this code:
#include <stdio.h>
#define OBSERVATION 7
#define MEDIAN 34
int main() {
float temp[OBSERVATION] = {0};
printf("Insert the patient's temperature over the course of 7 days: ");
for(int i = 1; i <= OBSERVATION; i++){
scanf("%f", &temp[i]);
}
printf("DAY\tVALUE\tISTOGRAM\n");
for(int i = 1; i <= OBSERVATION; i++){
printf("%6d\t%6g\n", i, temp[i]);
}
for(int i = 1; i <= OBSERVATION; i++){
switch ((int)temp[i] - MEDIAN) {
case 0: break;
case 1: printf("\t\t\t\t*");
break;
case 2: printf("\t\t\t\t**");
break;
case 3: printf("\t\t\t\t***");
break;
case 4: printf("\t\t\t\t****");
break;
case 5: printf("\t\t\t\t*****");
break;
case 6: printf("\t\t\t\t******");
break;
case 7: printf("\t\t\t\t*******");
break;
case 8: printf("\t\t\t\t********");
break;
case 9: printf("\t\t\t\t*********");
break;
case 10: printf("\t\t\t\t*********");
break;
case 11: printf("\t\t\t\t**********");
break;
case 12: printf("\t\t\t\t***********");
break;
}
printf("\n");
}
return 0;
}
The code compiles fine and outputs the first two columns correctly, but completely skips the switch statement. I've already tried to check if it erroneously assigns 0 to temp[i] when it gets cast to an int, but it doesn't do that. It simply skips the switch.
Also do you have a more "compact" way on how to print out the * column without using a switch?

Answer 1

I would rewrite your code like this:
#include <stdio.h>
#include "math.h"
#define OBSERVATION 7
#define MEDIAN 34
int main() {
float temp[OBSERVATION] = {0};
int iDifference = 0;
printf("Insert the patient's temperature over the course of 7 days: \n");
for(int i = 0; i < OBSERVATION; i++){
scanf("%f", &temp[i]);
}
then print the headers:
printf("DAY\tVALUE\tISTOGRAM\n");
start the row loop:
for(int i = 0; i < OBSERVATION; i++){
// calculate the difference integer
iDifference = round(temp[i] - MEDIAN);
// don't add stars if the temperature diff is lower than 0
if(iDifference < 0) iDifference = 0;
// print the first two columns, notice that the new line isn't added yet
printf("%6d\t%6.2f\t", i, temp[i]);
// print the stars
vDrawStars(iDifference);
// then write the newline character
printf("\n");
}
return 0;
}
then the drawing stars routine:
void vDrawStars(int prm_iCount){
int p = 0;
// I didn't understand the case for it but
// printf("\t\t\t\t");
// then draw the needed stars
for(p = 0; p < prm_iCount; p++)
{
printf("*");
}
// no new lines, still on the same line.
}
Here's a demo here: https://onlinegdb.com/BJPyvDJRX

Answer 2

Your code works incorrectly, because you access the array temp out of bounds. Array indexes start with zero, so you should index with for(int i = 0; i < OBSERVATION; i++).
The switch:
switch ((int)temp[i] - MEDIAN) {
case 0: break;
case 1: printf("\t\t\t\t*");
break;
case 2: printf("\t\t\t\t**");
break;
case 3: printf("\t\t\t\t***");
break;
case 4: printf("\t\t\t\t****");
break;
case 5: printf("\t\t\t\t*****");
break;
case 6: printf("\t\t\t\t******");
break;
case 7: printf("\t\t\t\t*******");
break;
case 8: printf("\t\t\t\t********");
break;
case 9: printf("\t\t\t\t*********");
break;
case 10: printf("\t\t\t\t*********");
break;
case 11: printf("\t\t\t\t**********");
break;
case 12: printf("\t\t\t\t***********");
break;
}
may be optimized just to:
const int val = (int)temp[i] - MEDIAN;
if (1 <= val && val <= 12) { // make sure it's between 1 and 12
printf("\t\t\t\t%.*s", val, "***********");
}
The printf format modifier "%.*s" takes two parameters - length of the string to print and the string itself
We print val length of "**********" characters.