数据结构之栈实现计算器

在终端输入一个表达式（四则运算及括号），计算表达式的值。

calculator.h

#ifndef __CALCULATOR_H__#define __CALCULATOR_H__#define TRUE 1#define FALSE 0#define MAX 100typedef int StackNum;typedef char StackOp;typedef struct _num{StackNum data;struct _num *next;}Num_node;typedef struct _op{StackOp data;struct _op *next;}Op_node;typedef struct _linkStack{Num_node *numtop;Op_node *optop;}LinkStack;//创建链式栈LinkStack * Create_Stack ();//判断操作数栈空int StackEmpty_num (LinkStack *s);//判断运算符栈空int StackEmpty_op (LinkStack *s);//进操作数栈int Push_num (LinkStack *s,StackNum num);//进运算符栈int Push_op (LinkStack *s,StackOp op);//出操作数栈int Pop_num (LinkStack *s,StackNum *num);//出运算符栈int Pop_op (LinkStack *s,StackOp *op);//获取运算符栈顶元素int GetTop_op (LinkStack *s,StackOp *op);//比较运算符优先级int Cmp_op (LinkStack *s,StackOp op);//运算int Operate (LinkStack *s);//销毁栈int Destory(LinkStack *s);#endif  //__CALCULATOR_H__

calculator.c

#include <stdlib.h>#include "calculator.h"#include "error.h"//创建链式栈LinkStack * Create_Stack (){LinkStack * s = (LinkStack *)malloc(sizeof(LinkStack)/sizeof(char));if (s == NULL){errno = MALLOC_ERROR;return NULL;}s->numtop = NULL;s->optop = NULL;return s;}//判断操作数栈空int StackEmpty_num (LinkStack *s){if (s == NULL){errno = ERROR;return FALSE;}return s->numtop == NULL;}//判断运算符栈空int StackEmpty_op (LinkStack *s){if (s == NULL){errno = ERROR;return FALSE;}return s->optop == NULL;}//进操作数栈int Push_num (LinkStack *s,StackNum num){if (s == NULL){errno = ERROR;return FALSE;}Num_node * num_node = (Num_node *)malloc(sizeof(Num_node)/sizeof(char));if (num_node == NULL){errno = MALLOC_ERROR;return FALSE;}num_node->data = num;num_node->next = s->numtop;s->numtop = num_node;return TRUE;}//进运算符栈int Push_op (LinkStack *s,StackOp op){if (s == NULL){errno = ERROR;return FALSE;}Op_node * op_node = (Op_node *)malloc(sizeof(Op_node)/sizeof(char));if (op_node == NULL){errno = MALLOC_ERROR;return FALSE;}op_node->data = op;op_node->next = s->optop;s->optop = op_node;return TRUE;}//出操作数栈int Pop_num (LinkStack *s,StackNum *num){if (s == NULL){errno = ERROR;return FALSE;}if (StackEmpty_num (s)){errno = EMPTY_STACK;return FALSE;}Num_node *p = s->numtop;*num = p->data;s->numtop = p->next;free(p);return TRUE;}//出运算符栈int Pop_op (LinkStack *s,StackOp *op){if (s == NULL){errno = ERROR;return FALSE;}if (StackEmpty_op (s)){errno = EMPTY_STACK;return FALSE;}Op_node *p = s->optop;*op = p->data;s->optop = p->next;free(p);return TRUE;}//获取运算符栈顶元素int GetTop_op (LinkStack *s,StackOp *op){if (s == NULL){errno = ERROR;return FALSE;}if (StackEmpty_op (s)){errno = EMPTY_STACK;return FALSE;}*op = s->optop->data;return TRUE;}//比较运算符优先级int Cmp_op (LinkStack *s,StackOp op){if (s == NULL){errno = ERROR;return FALSE;}if (StackEmpty_op (s)){return TRUE;}StackOp op2;GetTop_op (s,&op2);switch (op2){case '+':{return TRUE;}case '-':{if (op == '-' || op == '+'){return FALSE;}return TRUE;}case '*':{return FALSE;}case '/':{return FALSE;}default :return TRUE;}}//运算int Operate (LinkStack *s){if (s == NULL){errno = ERROR;return FALSE;}if (StackEmpty_op (s)){errno = EMPTY_STACK;return FALSE;}StackOp op;Pop_op (s,&op);if (op == '('){return FALSE;}StackNum num1,num2;Pop_num (s,&num1);if (StackEmpty_num (s)){Push_num (s,num1);return FALSE;}Pop_num (s,&num2);StackNum result;switch (op){case '+':result = num2 + num1;break;case '-':result = num2 - num1;break;case '*':result = num2 * num1;break;case '/':result = num2 / num1;break;default:return FALSE;}Push_num (s,result);return TRUE;}//销毁栈int Destory(LinkStack *s){if (s == NULL){errno = ERROR;return FALSE;}free(s);return TRUE;}

main.c

#include <stdio.h>#include "calculator.h"#include "error.h"#include <stdlib.h>int main(){LinkStack *s = Create_Stack ();char exp[MAX];printf ("input an expression:");fgets(exp,MAX,stdin);if (exp[0] < '0' || exp[0] > '9'){if (exp[0] != '('){errno = INPUT_ERROR;MyError ("fgets:");printf ("输入错误，第一个字符应该为数字或“(”\n");Destory(s);return FALSE;}}int i = 0;while (exp[i]){if (exp[i] == '\n'){exp[i] = '\0';break;}i++;}i = 0;char *p = exp;char *tmp = p;int flag = 0;while (p[i]){if (p[i] >= '0' && p[i] <= '9'){i++;flag = 1;continue;}if (flag == 1){Push_num (s,atoi(p));flag = 0;}p = &p[i];i = 0;if (p[i] == '('){if (p[i+1] == '+' || p[i+1] == '-' || p[i+1] == '*' || p[i+1] == '/' || p[i+1] == ')'){errno = INPUT_ERROR;MyError ("fgets:");Destory(s);return FALSE;}Push_op (s,'(');}else if (p[i] == ')'){while (Operate (s));}else{if (p[i+1] == '+' || p[i+1] == '-' || p[i+1] == '*' || p[i+1] == '/' || p[i+1] == ')'){errno = INPUT_ERROR;MyError ("fgets:");Destory(s);return FALSE;}while (Cmp_op (s,p[i]) != TRUE){Operate (s);}Push_op (s,p[i]);}p = &p[i+1];tmp = p;}if (flag == 1){Push_num (s,atoi(tmp));}while (Operate (s));StackNum result = 0;Pop_num (s,&result);printf ("result = %d\n",result);Destory(s);    return 0;}

此项目未完善的地方还有很多，特别是对一些错误输入的识别与处理。希望与大家一起完善。