方法一：常規方法

#include<stdio.h>

int Add(int a, int b)
{
	return a + b;
}
int Sub(int a, int b)
{
	return a - b;
}
int Mul(int a, int b)
{
	return a * b;
}
int Div(int a, int b)
{
	return a / b;
}

void menu()
{
	printf("****************************\n");
	printf("***** 1.add      2.sub *****\n");
	printf("***** 3.mul      4.div *****\n");
	printf("******     0.exit      *****\n");
	printf("****************************\n");
}
int main()
{
	int input = 1;
	int x = 0;
	int y = 0;
	int ret = 0;
	while (input)
	{
		menu();
		printf("請選擇：");
		scanf_s("%d", &input);
		if (input >= 1 && input <= 4)
		{
			printf("輸入兩個數：");
			scanf_s("%d%d", &x, &y);
		}
		switch (input)
		{
		case 1:
			ret = Add(x, y);
			break;
		case 2:
			ret = Sub(x, y);
			break;
		case 3:
			ret = Mul(x, y);
			break;
		case 4:
			ret = Div(x, y);
			break;
		case 0:
			printf("退出\n");
			break;
		default:
			printf("輸入錯誤\n");
			break;
		}
		printf("ret = %d\n", ret);
	}
	return 0;
}
 

方法二：函式指標陣列法

#include<stdio.h>

int Add(int a, int b)
{
	return a + b;
}
int Sub(int a, int b)
{
	return a - b;
}
int Mul(int a, int b)
{
	return a * b;
}
int Div(int a, int b)
{
	return a / b;
}

void menu()
{
	printf("****************************\n");
	printf("***** 1.add      2.sub *****\n");
	printf("***** 3.mul      4.div *****\n");
	printf("******     0.exit      *****\n");
	printf("****************************\n");
}
int main()
{
	int input = 1;
	int x = 0;
	int y = 0;
	int ret = 0;
	int(*p[5])(int, int) = { 0, Add, Sub, Mul, Div };   //有五個元素是為了方便標號對齊
	while (input)
	{
		menu();
		printf("請選擇：");
		scanf_s("%d", &input);
		if (input >= 1 && input <= 4)
		{
			printf("輸入兩個數：");
			scanf_s("%d%d", &x, &y);
			ret = p[input](x, y);
			printf("ret = %d\n", ret);
		}
	}
	return 0;
}
 

方法三：回撥函式法

#include<stdio.h>

int Add(int a, int b)
{
	return a + b;
}
int Sub(int a, int b)
{
	return a - b;
}
int Mul(int a, int b)
{
	return a * b;
}
int Div(int a, int b)
{
	return a / b;
}

void menu()
{
	printf("****************************\n");
	printf("***** 1.add      2.sub *****\n");
	printf("***** 3.mul      4.div *****\n");
	printf("******     0.exit      *****\n");
	printf("****************************\n");
}

void calc(int (*pfun) (int, int))
{
	int x = 0;
	int y = 0;
	int ret = 0;
	printf("輸入兩個數：");
	scanf_s("%d%d", &x, &y);
	ret = pfun(x, y);
	printf("ret = %d\n", ret);
}
int main()
{
	int input = 1;
	int(*p[5])(int, int) = { 0, Add, Sub, Mul, Div };
	while (input)
	{
		menu();
		printf("請選擇：");
		scanf_s("%d", &input);
		if (input >= 1 && input <= 4)
		{
			calc(p[input]);          //傳輸的是加減乘除函式的地址
		}
	}
	return 0;
}