Using range in switch case in C/C++

You all are familiar with switch case in C/C++, but did you know you can use a range of numbers instead of a single number or character in the case statement? Range in switch case can be useful when we want to run the same set of statements for a range of numbers so that we do not have to write cases separately for each value.

• That is the case range extension of the GNU C compiler and not standard C or C++
• You can specify a range of consecutive values in a single case label.

Syntax

The syntax for using range case is:

case low ... high:

It can be used for a range of ASCII character codes like this:

case 'A' ... 'Z':

You need to Write spaces around the ellipses ( … ). For example, write this:

// Correct  -   case 1 ... 5:
// Wrong -    case 1...5: 

C

// C program to illustrate
// using range in switch case
#include <stdio.h>
int main()
{
    int arr[] = { 1, 5, 15, 20 };

    for (int i = 0; i < 4; i++) {
        switch (arr[i]) {
            // range 1 to 6
        case 1 ... 6:
            printf("%d in range 1 to 6\n", arr[i]);
            break;
            // range 19 to 20
        case 19 ... 20:
            printf("%d in range 19 to 20\n", arr[i]);
            break;
        default:
            printf("%d not in range\n", arr[i]);
            break;
        }
    }
    return 0;
}

C++

// C++ program to illustrate
// using range in switch case
#include <iostream>
using namespace std;
int main()
{
    int arr[] = { 1, 5, 15, 20 };

    for (int i = 0; i < 4; i++) {
        switch (arr[i]) {
            // defining range 1 to 6
        case 1 ... 6:
            cout << arr[i] << " in range 1 to 6\n";
            break;
            // range 19 to 20
        case 19 ... 20:
            cout << arr[i] << " in range 19 to 20\n";
            break;
        default:
            cout << arr[i] << " not in range\n";
            break;
        }
    }
    return 0;
}

// This code is contributed by shivanisinghss2110

Output

1 in range 1 to 6
5 in range 1 to 6
15 not in range
20 in range 19 to 20

Complexity Analysis

• Time Complexity: O(n), where n is the size of array arr.
• Auxiliary Space: O(1)

Error conditions

1. low > high: The compiler gives an error message.
2. Overlapping case values: If the value of a case label is within a case range that has already been used in the switch statement, the compiler gives an error message.

Exercise

• You can try the above program for a char array by modifying the char array and case statement.

This article is contributed by Mandeep Singh. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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