//一般做法
#include<stdio.h>
#include<windows.h>
//#include<assert.h>
void menu()
{
?? ?printf("**************************\n");
?? ?printf("****歡迎來到計算器頁面****\n");
?? ?printf("**** 1.add ? ?2.mul ?*****\n");
?? ?printf("*****3.sub ? ?4.div1 *****\n");
?? ?printf("*****0.exit ? ? ? ? ?*****\n");
?? ?printf("**************************\n");
}

int add(int x, int y)
{
?? ?return x + y;
}

int mul(int x, int y)
{
?? ?return x * y;
}

int sub(int x, int y)
{
?? ?return x - y;
}

int div1(int x, int y)
{
?? ?return x / y;
}



int main()
{
?? ?int n = 1;
?? ?menu();
?? ?while (n)
?? ?{
?? ??? ?printf("請輸入選項:\n");
?? ??? ?scanf("%d", &n);
?? ??? ?int x = 0, y = 0;
?? ??? ?/*printf("請輸入兩個整數(shù)!\n");
?? ??? ?scanf("%d%d", &x, &y);*/ ? ?
? ? ? ? //若將兩個數(shù)字輸入放在此處會出現(xiàn)輸入錯誤時不能退出系統(tǒng)，而是顯示“輸入兩個整數(shù)”的提示
?? ??? ?switch (n)
?? ??? ?{
?? ??? ?case 1:
?? ??? ??? ?printf("請輸入兩個整數(shù)!\n");
?? ??? ??? ?scanf("%d%d", &x, &y);
?? ??? ??? ?printf("%d\n", add(x, y));
?? ??? ??? ?break;
?? ??? ?case 2:
?? ??? ??? ?printf("請輸入兩個整數(shù)!\n");
?? ??? ??? ?scanf("%d%d", &x, &y);
?? ??? ??? ?printf("%d\n", mul(x, y));
?? ??? ??? ?break;
?? ??? ?case 3:
?? ??? ??? ?printf("請輸入兩個整數(shù)!\n");
?? ??? ??? ?scanf("%d%d", &x, &y);
?? ??? ??? ?printf("%d\n", sub(x, y));
?? ??? ??? ?break;
?? ??? ?case 4:
?? ??? ??? ?printf("請輸入兩個整數(shù)!\n");
?? ??? ??? ?scanf("%d%d", &x, &y);
?? ??? ??? ?printf("%d\n", div1(x, y));
?? ??? ??? ?break;
?? ??? ?case 0:
?? ??? ??? ?printf("退出計算器！\n");
?? ??? ??? ?break;
?? ??? ?default:
?? ??? ??? ?printf("輸入錯誤，請重新輸入!\n");
?? ??? ?}
?? ?}
}

//使用函數(shù)指針數(shù)組解決計算器問題

#include<stdio.h>
#include<windows.h>
//#include<assert.h>

void menu()
{
?? ?printf("**************************\n");
?? ?printf("****歡迎來到計算器頁面****\n");
?? ?printf("**** 1.add ? ?2.mul ?*****\n");
?? ?printf("*****3.sub ? ?4.div1 *****\n");
?? ?printf("*****0.exit ? ? ? ? ?*****\n");
?? ?printf("**************************\n");
}

int add(int x, int y)
{
?? ?return x + y;
}

int mul(int x, int y)
{
?? ?return x * y;
}

int sub(int x, int y)
{
?? ?return x - y;
}

int div1(int x, int y)
{
?? ?return x / y;
}

int main()
{
?? ?int n = 1;
?? ?menu();
?? ?while (n)
?? ?{
?? ??? ?printf("請輸入選項:\n");
?? ??? ?scanf("%d", &n);
?? ??? ?int(*arr[5])() = { 0,add,mul,sub,div1 };//轉(zhuǎn)移表
? ? ? ? //定義一個函數(shù)指針數(shù)組，存放函數(shù)地址
?? ??? ?if (n >= 0 && n < 5)
?? ??? ?{
?? ??? ??? ?int x = 0, y = 0;
?? ??? ??? ?printf("請輸入兩個整數(shù):>\n");
?? ??? ??? ?scanf("%d%d", &x, &y);
?? ??? ??? ?printf("%d\n", (*arr[n])(x,y));//輸出結果
?? ??? ?}
?? ??? ?else
?? ??? ?{
?? ??? ??? ?printf("輸入有誤，請重新輸入!\n");
?? ??? ??? ?scanf("%d", &n);
?? ??? ?}
?? ?}
?? ?system("pause");
?? ?return 0;
}