Set Multiple Bits in 8-bit Register

Code

#include <stdio.h>
#include <stdint.h>

uint8_t set_range(uint8_t reg, uint8_t start, uint8_t end) {
    // Your code here
    int a=(end-start+1);
   uint16_t mask;
    switch (a){
        case 1:
            mask=0x01;
            break;
        case 2:
            mask=0x03;
            break;
        case 3:
            mask=0x07;
            break;
        case 4:
            mask=0x0F;
            break;
        case 5:
            mask=0x1F;
            break;
        case 6:
            mask=0x3F;
            break;
        case 7:
            mask=0x7F;
            break;
        case 0:
            mask=0x00;
            break;  
    }
    reg &= ~(mask << start); 
    reg |= ((0xFF & mask) << start); 
    

    return reg;
}

int main() {
    uint8_t reg, start, end;
    scanf("%hhu %hhu %hhu", &reg, &start, &end);
    printf("%u", set_range(reg, start, end));
    return 0;
}

Solving Approach