实现一个计算器涉及到了前缀表达式转后缀表达式。
分别定义两个栈，一个存数字，一个存操作符。
C++ 版本
#include "iostream"
#include <stack>
using namespace std;
int Priority(char ch)
{
switch(ch)
{
case '(':
return 3;
case '*':
case '/':
return 2;
case '+':
case '-':
return 1;
default:
return 0;
}
}
int main()
{
stack<char> s_opt;
stack<int> s_num;
char opt[1024] = {0};
int i = 0, tmp = 0, num1 = 0, num2 = 0;
cout << "Please input: " << endl;
cin >> opt;
while(opt[i] != '\0' || s_opt.empty() != true)
{
if(opt[i] >= '0' && opt[i] <= '9')
{
tmp = tmp * 10 + opt[i] - '0';
i++;
if(opt[i] > '9' || opt[i] < '0')
{
s_num.push(tmp);
tmp = 0;
}
}
else
{
if((opt[i] == ')') && (s_opt.top() == '('))
{
s_opt.pop();
i++;
continue;
}
if((s_opt.empty()) == true || (Priority(opt[i]) > Priority(s_opt.top())) ||
(s_opt.top() == '(' && (opt[i] != ')')))
{
s_opt.push( opt[i]);
i++;
continue;
}
if( ((opt[i] == '\0') &&( s_opt.empty() != true)) || ( (opt[i] == ')') && (s_opt.top() != '(') )||
(Priority(opt[i]) <= Priority(s_opt.top())) )
{
char ch = s_opt.top();
s_opt.pop();
int num1,num2;
switch(ch)
{
case'+':
num1 = s_num.top();
s_num.pop();
num2 = s_num.top();
s_num.pop();
s_num.push(num1 + num2);
break;
case'-':
num1 = s_num.top();
s_num.pop();
num2 = s_num.top();
s_num.pop();
s_num.push(num1 - num2);
break;
case'*':
num1 = s_num.top();
s_num.pop();
num2 = s_num.top();
s_num.pop();
s_num.push(num1 * num2);
break;
case'/':
num1 = s_num.top();
s_num.pop();
num2 = s_num.top();
s_num.pop();
s_num.push(num1 / num2);
break;
}
}
}
}
cout << s_num.top() << endl;
return 0;
}
C版本：
.h
#ifndef _LINKSTACK_H
#define _LINKSTACK_H
#define SUCCESS 10000
#define FAILURE 10001
#define TRUE 10002
#define FALSE 10003
#include <stdio.h>
#include <stdlib.h>
struct node
{
int date;
struct node *next;
};
typedef struct node Node;
struct stack
{
Node *top;
int count;
};
typedef struct stack Stack;
int LinkStackInit(Stack **s);
int LinkStackEmpty(Stack *s);
int Push(Stack **s,int e);
int GetTop(Stack *s);
int Pop(Stack **s);
int LinkStackClear(Stack **s);
int LinkStackDestory(Stack **s);
#endif
.c
#include "linkstack.h"
int LinkStackInit(Stack **s)
{
if(s == NULL)
{
return FAILURE;
}
(*s) = (Stack *)malloc(sizeof(Stack) * 1);
if(*s == NULL)
{
return FAILURE;
}
(*s) -> top = NULL;
(*s) -> count = 0;
return SUCCESS;
}
int LinkStackEmpty(Stack *s)
{
if(s == NULL)
{
return FAILURE;
}
return (s->top == NULL)? TRUE : FALSE;
}
int Push(Stack **s, int e)
{
if(s == NULL)
{
return FAILURE;
}
if((*s) == NULL)
{
return FAILURE;
}
Node *p = (Node *)malloc(sizeof(Node));
p -> date = e;
p -> next = (*s) -> top;
(*s) -> top = p;
(*s) -> count++;
return SUCCESS;
}
int GetTop(Stack *s)
{
if(s == NULL || s->top == NULL)
{
return FAILURE;
}
return s->top->date;
}
int Pop(Stack **s)
{
if(s == NULL || (*s) == NULL)
{
return FAILURE;
}
Node *p = (*s) -> top;
int e = (*s) -> top -> date;
(*s) -> top = (*s) -> top -> next;
(*s) -> count--;
free(p);
return e;
}
int LinkStackClear(Stack **s)
{
if(s == NULL || (*s) == NULL)
{
return FAILURE;
}
Node *temp = (*s) -> top;
while(temp != NULL)
{
(*s) -> top = temp -> next;
free(temp);
temp = (*s) -> top;
(*s)->count--;
}
return SUCCESS;
}
int LinkStackDestory(Stack **s)
{
if(s == NULL || (*s) == NULL)
{
return FAILURE;
}
free(*s);
(*s) = NULL;
return SUCCESS;
}
main.c
#include "linkstack.h"
int Priority(char ch)
{
switch(ch)
{
case '(':
return 3;
case '*':
case '/':
return 2;
case '+':
case '-':
return 1;
default:
return 0;
}
}
int main()
{
Stack *s_opt, *s_num;
char opt[1024] = {0};
int i = 0, tmp = 0, num1 = 0, num2 = 0;
if(LinkStackInit(&s_opt) != SUCCESS || LinkStackInit(&s_num) != SUCCESS)
{
printf("Init Failure \n");
}
printf("Please input: \n");
scanf("%s",opt);
while(opt[i] != '\0' || LinkStackEmpty(s_opt) != TRUE)
{
if(opt[i] >= '0' && opt[i] <= '9')
{
tmp = tmp * 10 + opt[i] - '0';
i++;
if(opt[i] > '9' || opt[i] < '0')
{
Push(&s_num, tmp);
tmp = 0;
}
}
else
{
if((opt[i] == ')') && (GetTop(s_opt) == '('))
{
Pop(&s_opt);
i++;
continue;
}
if((LinkStackEmpty(s_opt) == TRUE) || (Priority(opt[i]) > Priority(GetTop(s_opt))) ||
( (GetTop(s_opt) == '(') && (opt[i] != ')')))
{
Push(&s_opt, opt[i]);
i++;
continue;
}
if( ((opt[i] == '\0') &&( LinkStackEmpty(s_opt) != TRUE)) || ( (opt[i] == ')') && (GetTop(s_opt) != '(') )||
(Priority(opt[i]) <= Priority(GetTop(s_opt))) )
{
switch(Pop(&s_opt))
{
case'+':
num1 = Pop(&s_num);
num2 = Pop(&s_num);
Push(&s_num, (num2 + num1));
break;
case'-':
num1 = Pop(&s_num);
num2 = Pop(&s_num);
Push(&s_num, (num2 - num1));
break;
case'*':
num1 = Pop(&s_num);
num2 = Pop(&s_num);
Push(&s_num, (num2 * num1));
break;
case'/':
num1 = Pop(&s_num);
num2 = Pop(&s_num);
Push(&s_num, (num2 / num1));
break;
}
}
}
}
printf("%d \n",GetTop(s_num));
return 0;
}