#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define MAX 2
#define COUNT_OF(x) (sizeof(x) / sizeof(0[x])) //length of arrays at compile time

struct Person {
char firstname[64];
char lastname[64];
int age;
};

int Person_cmp_firstname(const void* x, const void* y) {
    struct Person *ix = (struct Person *)x;
    struct Person *iy = (struct Person *)y;
    return strcmp(ix->firstname, iy->firstname);
    }


int Person_cmp_lastname(const void* x, const void* y ) {
    struct Person *ix = (struct Person *)x;
    struct Person *iy = (struct Person *)y;
    return strcmp(ix->lastname, iy->lastname);
}
int Person_cmp_age(const void* x, const void* y) {
    struct Person *px = (struct Person *) x;
    struct Person *py = (struct Person *) y;
    return px->age - py->age;
}

int main(){;
    int choice;
    struct Person *P[10];
    printf("t***PROGRAM TO SORT PERSONS***nn");
    for(int i=0; i<3; i++){
        P[i] = (struct Person *) malloc(sizeof(struct Person));
        printf("Firstname: ");
        scanf("%s", P[i]->firstname);
        printf("Lastname: ");
        scanf("%s", P[i]->lastname);
        printf("Age: ");
        scanf("%d", &P[i]->age);
        printf("t***NEXT PERSON***nn");
    }
    do{
        printf("nt***CHOOSE HOW TO SORT***nntBy firstname: 1ntBy lastname: 2ntBy age: 3ntExit Program: 4nn");
        scanf("%d", &choice);
        switch(choice){
            case 1:
                printf("t***SORTING BY FIRSTNAME...***nn");
                qsort(P, COUNT_OF(P), sizeof(struct Person), Person_cmp_firstname);
                printf("t***DONE***nn");
                for(unsigned int i=0; i<3; i++){
                    printf( "Firstname: %st| Lastname: %st| Age: %dn", P[i]->firstname, P[i]->lastname, P[i]->age );
                }
                break;
            case 2:
                printf("t***SORTING BY LASTNAME...***nn");
                qsort(P, COUNT_OF(P), sizeof(struct Person ), Person_cmp_lastname);
                printf("t***DONE***nn");
                for(unsigned int i=0; i<3; i++){
                    printf( "Firstname: %st| Lastname: %st| Age: %dn", P[i]->firstname, P[i]->lastname, P[i]->age );
                }
                break;
            case 3:
                printf("t***SORTING BY AGE...***nn");
                qsort(P, COUNT_OF(P), sizeof(struct Person), Person_cmp_age);
                printf("t***DONE***nn");
                for(unsigned int i=0; i<3; i++){
                    printf( "Firstname: %st| Lastname: %st| Age: %dn",P[i]->firstname, P[i]->lastname, P[i]->age );
                }
                break;
            case 4:
                printf("t***EXITING PROGRAM***nn");
                for (int j = 0; j < 3; j++) {
                    free(P[j]);
                }
                exit(0);
            default:
                printf("t***INVALID OPTION***nn");
                break;
        }
    }while(1);
    return EXIT_SUCCESS;
}