C语言简易计算器（中缀表达式转后缀表达式，通过堆栈实现）

用C语言，写了一个简易的计算器，只有加减乘除，没有括号，但是若果要实现括号也是很容易的。

其核心思想是将输入的中缀表达式转换为后缀表达式，转换的思想主要参考了这位大牛的博客：http://blog.csdn.net/ssjhust123/article/details/8001651。

例如：输入中缀表达式2+2*3/2-1，程序可将其转换成后缀表达式2,2,3,2,/,*,+,1,-  其中','是为了间隔开数字，便于提取。最终的输出结果为：4

第一次发帖，本人菜鸟，欢迎高手批评指正！

代码如下：

#include "stdio.h"#include "string.h"#include "malloc.h"typedef struct tag_STACK_STRU{float valueData;struct tag_STACK_STRU *pNext;}stackList;//用链表实现数据的存储stackList *g_stOperand = NULL;//操作数stackList *g_stOperator = NULL;         //操作符void makeEmpty(stackList *stack);//清空栈char isEmpty(stackList *stack);//判断栈是否为空void push(stackList *stack, float data);//入栈操作void pop(stackList *stack);//出栈操作void calculate(char *p);//计算的子程序void changeStr(char *p);//将中缀表达式转换为后缀表达式char suffixStr[1024];int main(){// 业务代码实现处char *p = (char *)malloc(sizeof(char));g_stOperand = (stackList *)malloc(sizeof(stackList));g_stOperand->pNext = NULL;makeEmpty(g_stOperand);g_stOperator = (stackList *)malloc(sizeof(stackList));g_stOperator->pNext = NULL;makeEmpty(g_stOperator);scanf("%s",p);//获取输入的中缀表达式changeStr(p);//将中缀表达式转换成后缀表达式calculate(suffixStr);//通过后缀表达式进行计算printf("%d", (int)g_stOperand->pNext->valueData);//打印出最后结果//while(1);return 0;}//清空栈的操作void makeEmpty(stackList *stack){if (stack == NULL)printf("must creat stack first");while(!isEmpty(stack))pop(stack);}//判断栈是否为空char isEmpty(stackList *stack){return (stack->pNext == NULL);}//入栈操作void push(stackList *stack, float data){stackList *pTemp = (stackList *)malloc(sizeof(stackList));if (stack == g_stOperand)//操作数入栈{if (pTemp == NULL)return;pTemp->valueData = data;pTemp->pNext = stack->pNext;stack->pNext = pTemp;}if (stack == g_stOperator)//操作符入栈{if (pTemp == NULL)return;pTemp->valueData = data;pTemp->pNext = stack->pNext;stack->pNext = pTemp;}}//出栈操作void pop(stackList *stack){stackList *pTop = NULL;if (isEmpty(stack))return;pTop = stack->pNext;stack->pNext = stack->pNext->pNext;free(pTop);}//计算void calculate(char *p){float a, b, t;char temp[100];int i = 0;makeEmpty(g_stOperand);makeEmpty(g_stOperator);while(*p){if((*p >= '0') && (*p <= '9')){while((*p >= '0') && (*p <= '9')){temp[i] = *p;p++;i++;}push(g_stOperand, atoi(temp));memset(temp, 0, sizeof(temp));i = 0;}if (*p == '+'){a = g_stOperand->pNext->valueData;pop(g_stOperand);b = g_stOperand->pNext->valueData;pop(g_stOperand);t = b + a; push(g_stOperand, t);}if (*p == '-'){a = g_stOperand->pNext->valueData;pop(g_stOperand);b = g_stOperand->pNext->valueData;pop(g_stOperand);t = b - a;push(g_stOperand, t);}if (*p == '*'){a = g_stOperand->pNext->valueData;pop(g_stOperand);b = g_stOperand->pNext->valueData;pop(g_stOperand);t = b * a;push(g_stOperand, t);}if (*p == '/'){a = g_stOperand->pNext->valueData;pop(g_stOperand);b = g_stOperand->pNext->valueData;pop(g_stOperand);t = b / a;push(g_stOperand, t);}p++;}}void changeStr(char *p){stackList *k = (stackList *)malloc(sizeof(stackList));int i = 0;k = g_stOperator;while(*p){if((*p >= '0') && (*p <= '9')){while((*p >= '0') && (*p <= '9')){suffixStr[i] = *p;p++;i++;}suffixStr[i++] = ',';}/* '+' -------  1'-' -------  2'*' -------  5'/' -------  6*/if (*p == '+'){if ( ( isEmpty(g_stOperator) ) )push(g_stOperator, 1);else if ( (g_stOperator->pNext->valueData - 1) > 2 ){while ( !isEmpty(g_stOperator) ){switch ((int)g_stOperator->pNext->valueData){case 1: suffixStr[i++] = '+'; suffixStr[i++] = ','; break;case 2: suffixStr[i++] = '-'; suffixStr[i++] = ','; break;case 5: suffixStr[i++] = '*'; suffixStr[i++] = ','; break;case 6: suffixStr[i++] = '/'; suffixStr[i++] = ','; break;}pop(g_stOperator);}push(g_stOperator, 1);}elsepush(g_stOperator, 1);p++;}if (*p == '-'){if ( ( isEmpty(g_stOperator) ) )push(g_stOperator, 2);else if ( (g_stOperator->pNext->valueData - 1) > 2 ){while ( !isEmpty(g_stOperator) ){switch ((int)g_stOperator->pNext->valueData){case 1: suffixStr[i++] = '+'; suffixStr[i++] = ','; break;case 2: suffixStr[i++] = '-'; suffixStr[i++] = ','; break;case 5: suffixStr[i++] = '*'; suffixStr[i++] = ','; break;case 6: suffixStr[i++] = '/'; suffixStr[i++] = ','; break;}pop(g_stOperator);}push(g_stOperator, 2);}elsepush(g_stOperator, 2);p++;}if (*p == '*'){push(g_stOperator, 5);p++;}if (*p == '/'){push(g_stOperator, 6);p++;}}while ( !isEmpty(g_stOperator) ){switch ((int)g_stOperator->pNext->valueData){case 1: suffixStr[i++] = '+'; suffixStr[i++] = ','; break;case 2: suffixStr[i++] = '-'; suffixStr[i++] = ','; break;case 5: suffixStr[i++] = '*'; suffixStr[i++] = ','; break;case 6: suffixStr[i++] = '/'; suffixStr[i++] = ','; break;}pop(g_stOperator);}}