12934 - Rotate Numbers

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

void rotatefun(int, int*, int*);
int main(){
    char arr[105] = {};
    int num[105] = {}, new_num[105] = {};
    int rotate = 1;
    scanf("%s", arr);
    int len = strlen(arr);
    for(int i = 0; i < len; i++){
        // change a string array with number and put it into a new int array
        num[i] = arr[i] - '0';
    }
    //for(int i = 0; i < len; i++) printf("%d", num[i]);

    for(int i = 0; i < len; i++){
        if(num[i] == 2 || num[i] == 3 || num[i] == 4 || num[i] == 7 ){
            rotate = 0;
            break;
        }
        else rotate = 1;
    }

    if(rotate == 0) printf("No\n");
    else {
        rotatefun(len, num, new_num);
    }
    return 0;
}

void rotatefun(int len, int *num, int *new_num){
    for(int i = 0; i < len; i++){
        if(num[i] == 6) num[i] = 9;
        else if(num[i] == 9) num[i] = 6;
    }

    for(int j = 0; j < len; j++){
        new_num[j] = num[len - 1 - j];
        //printf("%d\n", new_num[j]);
    }

    int k = 0;
    int zero = 0;
    //deleting leading zeroes
    while(k != len){
        if(new_num[k] == 0){
            zero = 1;
            k++;
            continue;
        } else if(new_num[k] != 0){
            break;
        }
    }
    //printf("k = %d ", k);
    if(zero == 1){
        for(int m = k; m < len - 1;m++){
            // starts from k-th element, delete leading zero
            printf("%d", new_num[m]);
        }
        printf("%d\n", new_num[len - 1]);
    } else if (zero == 0){
        for(int m = 0; m < len - 1; m++){
            // starts from element 0 because no leading zero
            printf("%d", new_num[m]);
        }
        printf("%d\n", new_num[len - 1]);
    }

    return;
}