C++实现中缀表达式求值代码

#include<iostream>
#include<cstring>
using namespace std;
#define maxSize 120
char buffer[maxSize];//表达式的最长长度
char strToken[maxSize];
typedef struct line{
unsigned short id;
short indexOfTable;
};
struct line data[maxSize];
int intTable[maxSize];
short flagOfIntTable = 0;
short flagOfStruct = 0;

struct line stackOfEP[maxSize];//存储后缀表达式
short stackOfID[maxSize];//存放符号
short countOfEP = 0;
short countOfID = 0;

const  short INTEGER = 1;
const short LEFT_B = 3;
const short RIGHT_B = 4;
const short PLUS =  6;
const short MINUX = 7;

const short MULTIPLY = 9;
const short DIVIDE = 10;

void deleBlank(const char* str){//将字符串空格清除
char *temp = buffer;
if(0 == *str){
*temp = '\0';
}
while(*str){
if(*str ==' '){
str++;
continue;
}
*temp++ = *str++;
}
*temp = '\0';
}
void init(char *str){
for(short i = 0;i <=strlen(str);i++){
*str = 0;
}
}
void wordAnalyse(const char* str){
const char *start = str;//字符开始指针
const char *search;//搜索指针
char *temp;
while(*start){
search = start;
temp = strToken;//循环一次，temp指针重新纠正为指向strToken首地址。
if(isdigit(*search) != 0){//是数字的时候返回值是4
while(isdigit(*search) != 0){
*temp++ = *search++;
}
*temp = '\0';
intTable[flagOfIntTable] = atoi(strToken);
//转换字符串成int型，atof();itoa(int value,char*s1,int radix)
data[flagOfStruct].id = INTEGER;
data[flagOfStruct].indexOfTable = flagOfIntTable;
init(strToken);//重新初始化
flagOfStruct++;
flagOfIntTable++;
start = search;
}
else if(*start == '+'){
data[flagOfStruct].id = PLUS;
data[flagOfStruct].indexOfTable = -1;
flagOfStruct++;
start++;
}
else if(*start == '-'){
data[flagOfStruct].id = MINUX;
data[flagOfStruct].indexOfTable = -1;
flagOfStruct++;
start++;
}
else if(*start == '*'){
data[flagOfStruct].id = MULTIPLY;
data[flagOfStruct].indexOfTable = -1;
flagOfStruct++;
start++;
}
else if(*start == '/'){
data[flagOfStruct].id = DIVIDE;
data[flagOfStruct].indexOfTable = -1;
flagOfStruct++;
start++;
}
else if(*start == '('){
data[flagOfStruct].id = LEFT_B;
data[flagOfStruct].indexOfTable = -1;
flagOfStruct++;
start++;
}
else if(*start == ')'){
data[flagOfStruct].id = RIGHT_B;
data[flagOfStruct].indexOfTable = -1;
flagOfStruct++;
start++;
}
else{start++;}
}
}

void traverse(){//将中缀表达式转化成后缀表达式

for(int i = 0;i <flagOfStruct;i++){
if(data[i].id == INTEGER){
stackOfEP[countOfEP++] = data[i];//如果是数字，直接压入后缀表达式。
}
else if(data[i].id >=PLUS&&data[i].id <= DIVIDE){//如果是运算符号

while(true){
if(countOfID == 0){
stackOfID[countOfID++] = data[i].id;
break;
}
else if(data[i].id - stackOfID[countOfID] >= 2){
stackOfID[countOfID++] = data[i].id;//入栈
break;
}
else{
stackOfEP[countOfEP].id = stackOfID[--countOfID];//出栈
stackOfEP[countOfEP].indexOfTable = -1;
countOfEP++;
}
}

}
else if(data[i].id == LEFT_B){//
stackOfID[countOfID++] = data[i].id;
}
else if(data[i].id == RIGHT_B){
while(true){
//直到有左括号，则弹出循环
if(stackOfID[countOfID-1] == LEFT_B){//必须减一，不然逻辑错误。
countOfID--;//出栈
break;
}
if(countOfID == 0){
break;
}
stackOfEP[countOfEP].id = stackOfID[--countOfID];
stackOfEP[countOfEP].indexOfTable = -1;
countOfEP++;
}
}
}
//数据输入结束时，释放所有符号栈的内容，并添加到后缀式
while(countOfID){
stackOfEP[countOfEP].id = stackOfID[--countOfID];
stackOfEP[countOfEP].indexOfTable = -1;
countOfEP++;
}

}

//计算后缀表达式
int compute(){
short tempPtr = 0;
int number[120];
for(int i = 0;i <countOfEP;i++){
if(stackOfEP[i].id == INTEGER){
number[tempPtr++] = intTable[stackOfEP[i].indexOfTable];
}
else if(stackOfEP[i].id == PLUS){
int a = number[--tempPtr];
int b = number[--tempPtr];
number[tempPtr++] = b + a;
}
else if(stackOfEP[i].id == MINUX){
int a = number[--tempPtr];
int b = number[--tempPtr];
number[tempPtr++] = b - a;
}
else if(stackOfEP[i].id == MULTIPLY){
int a = number[--tempPtr];
int b = number[--tempPtr];
number[tempPtr++] = b * a;
}
else if(stackOfEP[i].id == DIVIDE){
int a = number[--tempPtr];
int b = number[--tempPtr];
number[tempPtr++] = b/a;
}
}
return *number;
}
void display(){
for(int i = 0;i <flagOfStruct;i++){
if(data[i].id == INTEGER){printf("%d",intTable[data[i].indexOfTable]);}
else if(data[i].id == PLUS){printf("+");}
else if(data[i].id == MINUX){printf("-");}
else if(data[i].id == MULTIPLY){printf("*");}
else if(data[i].id == DIVIDE){printf("/");}
else if(data[i].id == LEFT_B){printf("(");}
else if(data[i].id == RIGHT_B){printf(")");}
else{printf("\n");}
}
}
void displayEP(){
for(int i = 0;i <countOfEP;i++){
if(stackOfEP[i].id == INTEGER){printf("%d",intTable[stackOfEP[i].indexOfTable]);}
else if(stackOfEP[i].id == PLUS){printf("+");}
else if(stackOfEP[i].id == MINUX){printf("-");}
else if(stackOfEP[i].id == MULTIPLY){printf("*");}
else if(stackOfEP[i].id == DIVIDE){printf("/");}
else if(stackOfEP[i].id == LEFT_B){printf("(");}
else if(data[i].id == RIGHT_B){printf(")");}
else{printf("\n");}
}
}
int main(){
//test wordAnalytse()
char str[20] = "12+3*  (8/2)";
deleBlank(str);
//printf(buffer);
wordAnalyse(buffer);
traverse();
displayEP();
printf("\n");
printf("%d\n",compute());
return 0;
}