LinuxC小练习——计算器

n栈在表达式计算过程中的应用 ：建立操作数栈和运算符栈。运算符有优先级。规则：

n自左至右扫描表达式，凡是遇到操作数一律进操作数栈。

n当遇到运算符时，如果它的优先级比运算符栈栈顶元素的优先级高就进栈。反之，取出栈顶运算符和操作数栈栈顶的连续两个操作数进行运算，并将结果存入操作数栈，然后继续比较该运算符与栈顶运算符的优先级。

n左括号一律进运算符栈，右括号一律不进运算符栈，取出运算符栈顶运算符和操作数栈顶的两个操作数进行运算，并将结果压入操作数栈，直到取出左括号为止。

#include "calculator.h"#include <stdio.h>int main(){LinkStack *s = Create_Stack();char str[100];int i = 0;char *pstr = str;char *pnum = str;printf("Please input an expression:");fgets(str,100,stdin);while(str[i]){if(str[i] == '\n'){str[i] = '\0';break;}i++;}int tmp = 0;while(*pstr){if(*pstr >= 'a' && *pstr <= 'z' ||\*pstr >= 'A' && *pstr <= 'Z'){tmp = 1;}pstr++;}if(tmp == 1){errno = INPUT_ERROR;myError("输入错误");return FALSE;}pstr = str;int flag = 0;while(*pstr){if(*pstr >= '0' && *pstr <= '9'){flag = 1;pstr++;continue;}else{if(flag == 1){numPush(s,atoi(pnum));flag = 0;}if(*pstr == '('){opPush(s,*pstr);}else if(*pstr == ')'){while(operate(s));}else{while(cmp_op(s,*pstr) != TRUE){operate(s);}opPush(s,*pstr);}pnum = pstr + 1;}pstr++;}if(flag == 1){numPush(s,atoi(pnum));}while(operate(s));int result;numPop(s,&result);printf("result = %d\n",result);    return 0;}

#ifndef __CALCULATOR_H__#define __CALCULATOR_H__#include "error.h"#define TRUE  1#define FALSE 0typedef int num;typedef char op;typedef struct _numnode{num data;struct _numnode *next;}numNode;typedef struct _opnode{op data;struct _opnode *next;}opNode;typedef struct _linkstack{numNode *numtop;opNode  *optop;}LinkStack;//创建链式栈LinkStack *Create_Stack();//判断操作数是不是空栈int numEmpty(LinkStack *s);//判断操作符是不是空栈int opEmpty(LinkStack *s);//操作数进栈int numPush(LinkStack *s,num x);//操作符进栈int opPush(LinkStack *s,op x);//操作数出栈int numPop(LinkStack *s,num *x);//操作符出栈int opPop(LinkStack *s,op *x);//取操作符栈顶元素int GetopTop(LinkStack *s,op *x);int cmp_op(LinkStack *s,op op2);int operate(LinkStack *s);#endif // __CALCULATOR_H__

#include "calculator.h"#include <stdlib.h>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;}int numEmpty(LinkStack *s)//判断num是否空栈{if(s ==NULL){errno = ERROR;return FALSE;}return s->numtop == NULL;}int opEmpty(LinkStack *s){if(s ==NULL){errno = ERROR;return FALSE;}return s->optop == NULL;}int numPush(LinkStack *s,num x){if(s ==NULL){errno = ERROR;return FALSE;}numNode *numnode =(numNode *)malloc(sizeof(numNode) / sizeof(char));if(numnode == NULL){errno = MALLOC_ERROR;return FALSE;}numnode->data = x;numnode->next = s->numtop;s->numtop = numnode;return TRUE;}int opPush(LinkStack *s,op x){if(s ==NULL){errno = ERROR;return FALSE;}opNode *opnode =(opNode *)malloc(sizeof(opNode) / sizeof(char));if(opnode == NULL){errno = MALLOC_ERROR;return FALSE;}opnode->data = x;opnode->next = s->optop;s->optop = opnode;return TRUE;}int numPop(LinkStack *s,num *x){if(s ==NULL){errno = ERROR;return FALSE;}if(numEmpty(s)){errno = EMPTY_STACK;return FALSE;}numNode *p = s->numtop;*x = p->data;s->numtop = p->next;free(p);return TRUE;}int opPop(LinkStack *s,op *x){if(s ==NULL){errno = ERROR;return FALSE;}if(opEmpty(s)){errno = EMPTY_STACK;return FALSE;}opNode *p = s->optop;*x = p->data;s->optop = p->next;free(p);return TRUE;}int GetopTop(LinkStack *s,op *x){if(s ==NULL){errno = ERROR;return FALSE;}if(opEmpty(s)){errno = EMPTY_STACK;return FALSE;}*x = s->optop->data;return TRUE;}int cmp_op(LinkStack *s,op op2){if(s ==NULL){errno = ERROR;return FALSE;}if(opEmpty(s)){return TRUE;}char op1;GetopTop(s,&op1);switch(op1){case '+':return TRUE;case '-':if(op2 == '-' || op2 == '+')return FALSE;elsereturn TRUE;case '*':return FALSE;case '/':return FALSE;default:return TRUE;}}int operate(LinkStack *s){if(s ==NULL){errno = ERROR;return FALSE;}if(opEmpty(s)){errno = EMPTY_STACK;return FALSE;}char op1;opPop(s,&op1);if(op1 == '('){return FALSE;}int num1,num2;numPop(s,&num1);numPop(s,&num2);int result;switch(op1){case '+':result = num1 + num2;break;case '-':result = num1 - num2;break;case '*':result = num1 * num2;break;case '/':result = num1 / num2;break;default:result = 0;break;}numPush(s,result);return TRUE;}

#ifndef __ERROR_H__#define __ERROR_H__#include <stdio.h>#define ERROR        -1#define EMPTY_STACK  -2#define FULL_STACK   -3#define MALLOC_ERROR -4#define FULL_QUEUE   -5#define EMPTY_QUEUE  -6#define INPUT_ERROR  -7int errno;void myError(char *str); char *myStrError(int num);#endif //__ERROR_H__

#include "error.h"void myError(char *str){char *msg = myStrError(errno);printf("%s:%s\n",str,msg);}char* myStrError(int num){switch(errno){case ERROR:return "输入参数错误";case FULL_STACK:return "满栈状态";case EMPTY_STACK:return "空栈状态";case MALLOC_ERROR:return "空间分配失败";case FULL_QUEUE:return "队满";case EMPTY_QUEUE:return "队空";case INPUT_ERROR:return "输入字母";}}