How to calculate area of geometric shapes

Question

I created a program that calculates Area of geometric shapes. At the beginning it asks user to enter a letter to select the shape for which he wants to calculate the area. Letters don't work I don't know why so I use numbers instead. Can anyone help me with that?

int letter;
printf("1 for triangle\n2 for square\n3 for rectangle: ");
scanf("%d", &letter);
if (letter == 1)
...

I want it to be like t for triangle, s for square and so on.

If you were using letters and the `%c` format specifier please see [scanf() leaves the newline char in the buffer](https://stackoverflow.com/questions/5240789/scanf-leaves-the-new-line-char-in-the-buffer). Try `scanf(" %c", &shape);` with a space before the `%`. — Weather Vane, Jan 01 '21 at 19:40
So, the problem is that you want to do it with letters right? The current example is working? — Matteo Pinna, Jan 01 '21 at 19:45
yes i want it like if (letter == s) than it calculate square area — Farouk Info, Jan 01 '21 at 19:46

Matteo Pinna · Accepted Answer · 2021-01-01T20:19:58.220

0

You can do something like this, store your input string in a buffer and then check user choice with strcmp, which compares first argument with second one.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>


int main (void) {
    char s[3];
    
    printf("Choose geometric shape: <t> for triangle | <s> for square | <r> for rectangle\n");
    scanf(" %s",s);
    
    if (strcmp(s, "t")==0) {
         printf("TRIANGLE\n");
        /* do stuff */
    }
    else if (strcmp(s, "r")==0) {
        printf("RECTANGLE\n");
        /* do stuff */
    }
    else if (strcmp(s, "s")==0) {
        printf("SQUARE\n");
        /* do stuff */
    }
    else {
        printf("Unknown input\n");
    }
    
    return 0;
}

edited Jan 01 '21 at 20:19

answered Jan 01 '21 at 20:07

Matteo Pinna

409
4
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1

Why not to use `char c` and `if( c == 't' )` instead? – anotherOne Jan 01 '21 at 20:25
`char s[3]; scanf(" %s",s);` is begging a buffer overflow accident or exploit. – Weather Vane Jan 01 '21 at 20:45

How to calculate area of geometric shapes

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