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#include

#include

#include

struct Numerical

{

double value;

struct Numerical *next;

};

struct Symbol

{

char c;

struct Symbol *next;

};

void Push_Numerical(struct Numerical **top,double value)

{

struct Numerical *p = *top;

(*top = (struct Numerical*)malloc(sizeof (struct Numerical)))->next = p;

(*top)->value = value;

}

void Push_Symbol(struct Symbol **top,char c)

{

struct Symbol *p = *top;

(*top = (struct Symbol*)malloc(sizeof (struct Symbol)))->next = p;

(*top)->c = c;

}

double Pop_Numerical(struct Numerical **top)

{

struct Numerical *p = *top;

double n = (*top)->value;

*top = (*top)->next;

free(p);

return n;

}

char Pop_Symbol(struct Symbol **top)

{

struct Symbol *p = *top;

char c = (*top)->c;

*top = (*top)->next;

free(p);

return c;

}

int priority(char c)

{

switch (c)

{

case *+*:

case *-*:

return 1;

case ***:

case */*:

return 2;

default:

return 10;

}

}

double calculate(char c,double l,double g)

{

switch (c)

{

case *+*:

return l + g;

case *-*:

return l - g;

case ***:

return l * g;

case */*:

return l / g;

}

}

int main (void)

{

struct Numerical *Numerical_stack = NULL;

struct Symbol *Symbol_stack = NULL;

double n;

int last_number = 0; //上一个读取的是不是数则值为假，如果上一个读取的是数，下一个只能是读取字符

char pop_c,c;

puts("表达式计算器\n\n");

puts("1.作者很笨，写出来的程序智商很低，因此它是一个很单纯的计算器，请不要用复杂的算数表达式为难它\n");

puts("2.因为作者忘记了除数不能为0，所以并没有做特殊处理，请不要故意除以0\n");

puts("3.当你输入错误的表达式，程序会采用崩溃的方式提示你的输入有误，请重启程序重新输入\n");

puts("4.支持的运算符：英文状态下：‘(’‘)’‘+’‘-’‘*’‘/’\n");

puts("程序有些BUG，某些表达式会得出错误的结果，希望大家能够指出\n作者：642985327");

system("pause");

system("cls");

begin:

if((c = getchar()) == *-*)Push_Numerical(&Numerical_stack,0); //如：-(5)第一个字符被压栈双目运算数字栈空导致错误

ungetc(c,stdin);

while ((c = getchar())!= *\n*) //读取表达式内容，在转换后缀表达式的同时进行运算

{

ungetc(c,stdin);

if (last_number == 0 && scanf("%lf",&n))

{

Push_Numerical(&Numerical_stack,n);

last_number = 1;

}

else

{

char a = getchar();

if ((c == *+* || c == *-* ) && c != a && last_number != 1) //防止scanf吃掉正负号导致程序错误计算，如果scanf勿吃掉了计算用的正负号则仍回输入流

ungetc(a,stdin);

else

c=a;

if ((c) == *)*)

{

while ((pop_c = Pop_Symbol(&Symbol_stack)) != *(*)

{

double g = Pop_Numerical(&Numerical_stack);

double l = Pop_Numerical(&Numerical_stack);

Push_Numerical(&Numerical_stack,calculate(pop_c,l,g));

}

}

else if (Symbol_stack == NULL || c == *(* || Symbol_stack->c ==*(* || priority(Symbol_stack->c) < priority(c))

{

Push_Symbol(&Symbol_stack,c);

}

else

{

while (Symbol_stack->c != *(*)

{

pop_c = Pop_Symbol(&Symbol_stack);

double g = Pop_Numerical(&Numerical_stack);

double l = Pop_Numerical(&Numerical_stack);

Push_Numerical(&Numerical_stack,calculate(pop_c,l,g));

if (Symbol_stack == NULL || priority(Symbol_stack->c) < pop_c || Symbol_stack->c == *(*)break;

}

Push_Symbol(&Symbol_stack,c);

}

if (c != *)*)last_number = 0; //除了在读到*)*的情况，读到其他符号，下一次都能尝试读取一个数字

}

}

while (Symbol_stack != NULL) //剩余符号全部弹出栈参与运算

{

double g = Pop_Numerical(&Numerical_stack);

double l = Pop_Numerical(&Numerical_stack);

Push_Numerical(&Numerical_stack,calculate(Pop_Symbol(&Symbol_stack),l,g));

}

printf("%g\n",Pop_Numerical(&Numerical_stack));

goto begin

return 0;

}