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写一个程序，实现分数相加。用户以分子/分母的形式输入分数，程序打印相加后的结果。如：
输入:
5/6
3/4

输出：
The sum is 19/12
辗转相除法化简

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
// 定义SWAP宏函数，用来交换两个整数
#define SWAP(x, y) {	\
	int tmp = x;	\
	x = y;		\
	y = tmp;	\
}

int main(void) {
	int num1, denom1;
	printf("Enter first fraction: ");
	scanf("%d/%d", &num1, &denom1);

	int num2, denom2;
	printf("Enter second fraction: ");
	scanf("%d/%d", &num2, &denom2);

	int result_num = num1 * denom2 + num2 * denom1;
	int result_denom = denom1 * denom2;
	int result_gcd = gcd(result_num, result_denom);

	printf("The sum is %d/%d\n", result_num / result_gcd, result_denom / result_gcd);

	return 0;
}

// 用辗转相除法求最大公约数: gcd(a, b) = gcd(b, r)
int gcd(int a, int b) {
	if (a < b) {
		SWAP(a, b);
	}
	while (b != 0) {
		int r = a % b;
		a = b;
		b = r;
	}
	return a;
}