Biểu diễn phân số bằng struct

/***************************Complex****************************/
#include <stdio.h>
#include <conio.h>

typedef struct FraTag
{
int num;
int den;
}FRACTION;

int grst_comm_div(int a, int b);
int lst_comm_mult(int a, int b);
void fra_import(FRACTION* fra);
void fra_show(FRACTION fra, char name);
FRACTION fra_operator(FRACTION firstFra, FRACTION secondFra, char op);
FRACTION fra_reduce(FRACTION fra);

void main()
{
int sel;
char c;
FRACTION fract[2];
FRACTION resFra;
fra_import(&fract[0]);
fra_show(fract[0], '1');
fra_import(&fract[1]);
fra_show(fract[1], '2');

do
{
printf("\n\n1. Cong 2 phan so: C = A+B");
printf("\n2. Tru 2 phan so: C = A-B");
printf("\n3. Nhan 2 phan so: C = A*B");
printf("\n4. Chia 2 phan so: C = A/B");
printf("\nBan chon: ");
scanf("%d", &sel);

switch(sel)
{
case 1:
resFra = fra_operator(fract[0], fract[1], '+');
fra_show(resFra, '3');
break;
case 2:
resFra = fra_operator(fract[0], fract[1], '-');
fra_show(resFra, '3');
break;
case 3:
resFra = fra_operator(fract[0], fract[1], '*');
fra_show(resFra, '3');
break;
case 4:
resFra = fra_operator(fract[0], fract[1], '/');
fra_show(resFra, '3');
break;
}
printf("\nBan co muon tiep tuc ko: (y/n)?");
fflush(stdin);
c = getchar();
}
while( c == 'y' || c == 'Y');
getch();
}

// Ham tim USCLN
int greatest_common_divisor(int a, int b)
{
if(a == 0 && b == 0)
return -1;
else
return (b == 0)? a : greatest_common_divisor(b, a%b);
}

// Ham tim BSCNN
int lowest_common_multiple(int a, int b)
{
if(a == 0 || b == 0)
return -1;
else
return (a*b/greatest_common_divisor(a, b));
}

// Ham nhap phan so
void fra_import(FRACTION* fra)
{
printf("\nNhap vao tu so: ");
scanf("%d", &fra->num);
do
{
printf("\nNhap vao mau so: ");
scanf("%d", &fra->den);
}while(fra->den == 0);
}

// Ham tinh +, -, *, / 2 phan so
FRACTION fra_operator(FRACTION firstFra, FRACTION secondFra, char op)
{
FRACTION resFra;
int lowest_common_den;
int greatst_common_div;
switch(op)
{
case '+':
resFra.num = firstFra.num * secondFra.den +
secondFra.num * firstFra.den;
resFra.den = firstFra.den * secondFra.den;
resFra = fra_reduce(resFra);
break;
case '-':
resFra.num = firstFra.num * secondFra.den -
secondFra.num * firstFra.den;
resFra.den = firstFra.den * secondFra.den;
resFra = fra_reduce(resFra);
break;
case '*':
resFra.num = firstFra.num * secondFra.num;
resFra.den = firstFra.den * secondFra.den;
resFra = fra_reduce(resFra);
break;
case '/':
resFra.num = firstFra.num * secondFra.den;
resFra.den = firstFra.den * secondFra.num;
resFra = fra_reduce(resFra);
break;
default:
printf("\nToan tu khong hop le");
}
return resFra;
}

// Ham rut gon phan so
FRACTION fra_reduce(FRACTION fra)
{
FRACTION resFra;
int greatest_common_div = greatest_common_divisor(fra.num, fra.den);
resFra.num = fra.num/greatest_common_div;
resFra.den = fra.den/greatest_common_div;
return resFra;
}

// Show fraction
void fra_show(FRACTION fra, char name)
{
printf("\nPS(%c) = %d/%d", name, fra.num, fra.den);
}