数学运算后缀表达式转换成中缀表达式

#include <string.h> #include <iostream.h> #include <stdlib.h> #define MaxSize 32 typedef char Qelemtype; typedef struct { Qelemtype *base; //指向队列的存储空间； int front; //指向队头元素； int rear; //指向队尾元素的下一位置； }SqQueue; typedef struct LNode { int data; struct LNode *next; }Snode,*LinkStack; void DestroyLinStack(LinkStack &S) {//销毁链栈S。 LinkStack temp=S,p; while(temp) { p=temp; temp=temp->next; free(p); } } void Push(LinkStack &S, char x) {//入栈。 LinkStack temp=(LinkStack )malloc(sizeof(Snode )); temp->data=x; temp->next=S->next; S->next=temp; } void Pop(LinkStack &S, char &x) {//出栈。 LinkStack temp=S->next; x=temp->data; S->next=temp->next; free(temp); } int GetTop(LinkStack &S) {//读栈顶元素. int x; if(S->next) x=S->next->data; else cout<<"Stack Null "<<endl; return x; } void Initstack(LinkStack &S) { S=(LinkStack )malloc(sizeof(Snode )); if(!S) { cout<<"Alloctation Error"<<endl; exit(1); } S->next=0; } int InitQueue(SqQueue &Q) {//队列的初始化； Q.front=Q.rear=0; Q.base=(Qelemtype *)malloc(MaxSize*sizeof(Qelemtype)); if(!Q.base) exit(1); Q.base[Q.front]='\0'; return 1; } int QueueLength(SqQueue Q) {//计算队列的长度； return (Q.rear-Q.front+MaxSize)%MaxSize; } void EnQueue(SqQueue &Q, Qelemtype x) {//入队； if(QueueLength(Q)==MaxSize) { cout<<"EnQueue Error "<<endl; return ; } Q.base[Q.rear++]=x; } void DispQueue(SqQueue Q) {//输出队列的所有元素； int i=0,j=Q.front; while(i<QueueLength(Q)) { cout<<Q.base[j]; j++; i++; } } void DestroyQueue(SqQueue &Q) { //队列的销毁； delete []Q.base; Q.base=0; Q.front=Q.rear=0; return ; } int StackEmpty(LinkStack S) {//判断栈是否为空. return (S->next==0); } int Priority(char oper) { switch(oper) { case '(': return 0; case '+': case '-': return 1; case '*': case '/': return 2; } } void convertpostexp(char *str,SqQueue &post) { char c,t; int i=0,k=strlen(str); LinkStack S; Initstack(S); Push(S,'('); InitQueue(post); while(i<k || !StackEmpty(S)) { c=*str++; switch(c) { case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': EnQueue(post, c); break; case '(': Push(S,c); break; case ')': case ';': do{ Pop(S,t); if(t!='(') EnQueue(post, t); }while(t!='(' && !StackEmpty(S)); break; case '+': case '-': case '*': case '/': while(Priority(c)<=Priority(GetTop(S))) { Pop(S,t); EnQueue(post, t); } Push(S,c); break; } i++; } DestroyLinStack(S); } void main() { SqQueue post; char str[32]; cout<<"请输入计算表达式：(在最后要加上;)"<<endl; cin>>str; convertpostexp(str,post); cout<<"转换成后缀表达式是:"<<endl; DispQueue(post); cout<<endl; DestroyQueue(post); }