后缀表达式转化为前缀表达式并求值

#include <stdio.h>#include <stdlib.h>#include <string.h>#define STACK_INIT_SIZE 100#define STACKINCREMENT 10#define OK 1#define OVERFLOW -2#define ERROR 0#define TRUE 1#define FALSE 0typedef int Selemtype;typedef int Status;#define MAX 50char string1[MAX]; //定义两个字符串分别存放中缀表达式和后缀表达式char string2[MAX];int result;typedef struct{Selemtype *base; //在构造之前和销毁之后，base的值为NULLSelemtype *top; //栈顶指针int stacksize; //当前分配的存储空间，以元素为单位}SqStack;Status InitStack(SqStack *S);Status Push(SqStack *S,Selemtype e);Status Pop(SqStack *S,Selemtype e);Status InitStack(SqStack *S){ //构造一个空栈SS->base=(Selemtype*)malloc(STACK_INIT_SIZE*sizeof(Selemtype));if(!S->base) return OVERFLOW; //存储分配失败S->top=S->base;S->stacksize=STACK_INIT_SIZE;return OK;}Status Push(SqStack *S,Selemtype e){ //插入元素e为新的栈顶元素if(S->top-S->base>=S->stacksize){ //栈满，追加存储空间S->base=(Selemtype*)realloc(S->base,(S->stacksize+STACKINCREMENT)*sizeof(Selemtype));if(!S->base) return OVERFLOW; //存储分配失败S->top=S->base+S->stacksize;S->stacksize+=STACKINCREMENT;}*S->top++=e;return OK;}Status Pop(SqStack *S,Selemtype e){ //若栈不空值，则删除S的栈顶元素，用e返回其值，并返回OK,否则返回ERRORif(S->top==S->base) return ERROR;e=*--S->top;return OK;}Status StackEmpty(SqStack *S){ //若栈S为空，则返回TRUE,否则返回FALSEif(S->top==S->base)return TRUE;elsereturn FALSE;}Selemtype GetTop(SqStack *S){ //取栈顶元素并用e返回其值Selemtype e;if(S->top==S->base) return ERROR;e=*(S->top-1);return e;}void transform(char str1[],char str2[]){ //将中缀表达式转换为后缀表达式SqStack Op;InitStack(&Op); //定义一个空栈用来存放运算符Push(&Op,'#');Selemtype top; //取得运算符栈的栈顶元素赋值给topSelemtype e=NULL; //出栈的栈顶元素赋值给eint i=0,j=0,m;char a;m=strlen(str1);for(i=0;i<m;i++){a=str1[i];if('0'<=str1[i]&&str1[i]<='9') //如果是操作数直接放在后缀表达式中{str2[j]=str1[i];j++;}else{str2[j]=' ';j++;switch(a){case '(':{Push(&Op,a);} break;case '*':case '/':top=GetTop(&Op);if((top=='*')||(top=='/')){Pop(&Op,e);str2[j]=top;j++; //比其高，现将栈顶运算符出栈，再进栈。

Push(&Op,a);}else{Push(&Op,a);} break;case '+':case '-':top=GetTop(&Op);if(top=='+'||top=='-'||top=='*'||top=='/'){Pop(&Op,e);str2[j]=top;j++;Push(&Op,a);}else{Push(&Op,a);} break;case ')':{top=GetTop(&Op);Pop(&Op,e);while(top!='('){str2[j]=top;j++;top=GetTop(&Op);Pop(&Op,e);}} break;}}}top=GetTop(&Op);Pop(&Op,e);while(top!='#'){str2[j]=top;j++;top=GetTop(&Op);Pop(&Op,e);}str2[j]=top;printf("转化后的后缀表达式为:%s\n",str2);}Selemtype counttem(char str[]){ //计算后缀表达式的值SqStack S;InitStack(&S);int len;len=strlen(str);Selemtype A[10];int m,n,p,e=NULL,k,E;int i,j,l,ch,zh; //zh为字符型转化为的整形数for(i=0;i<len;i++){if('0'<str[i]&&str[i]<='9'){k=i;j=0;while('0'<=str[k]&&str[k]<='9') //将字符型的一串数字转化为整形{A[j]=str[k]-48;j++;k++;}ch=A[j-1];E=1;for(l=1;l<j;l++){E=10*E;zh=A[j-l-1]*E;ch+=zh;}Push(&S,ch);i=k-1;}else if(str[i]=='+'||str[i]=='-'||str[i]=='*'||str[i]=='/'){m=GetTop(&S);Pop(&S,e);n=GetTop(&S);Pop(&S,e);switch (str[i]){case'+':p=m+n; break;case'-':p=n-m; break;case'*':p=n*m; break;case'/':p=n/m; break;}Push(&S,p);}else if(str[i]==' '){}else if(str[i]=='#'){result=GetTop(&S);}}printf("表达式的运算结果为：%d\n",result);return result;}void main(){printf("请输入表达式（整数的四则运算）");gets(string1); //用字符串string1盛放中缀表达式transform(string1,string2); //用字符串string2盛放后缀表达式counttem(string2);}。