中缀表达式转后缀表达式

中缀表达式转后缀表达式

2015-04-05 Lover雪儿

  1 //中缀表达式转换为后缀表达式(逆波兰表达式)

  2 #include <stdio.h>

  3 #include <stdlib.h>

  4 #include <math.h>

  5 #include <ctype.h>

  6 

  7 #define STACK_INIT_SIZE        20    //初始栈大小

  8 #define STACK_INCREMENT        10  //扩充栈时每次增加的内存

  9 #define MAXBUFFER            10  //缓冲区

 10 

 11 typedef char ElemType;            //栈中的数据类型

 12 typedef struct {

 13     ElemType *base;

 14     ElemType *top;

 15     int stackSize;

 16 }sqStack;

 17 

 18 //初始化栈

 19 void init_stack(sqStack *s){

 20     s->base = (ElemType *)malloc(STACK_INIT_SIZE * sizeof(ElemType));

 21     if(!s->base)

 22         exit(-1);

 23     s->top = s->base;

 24     s->stackSize = STACK_INIT_SIZE;

 25 }

 26 //入栈

 27 void push(sqStack *s,ElemType e){

 28     if(s->top - s->base >= s->stackSize){    //检测栈是否已满

 29         //若是已满，则自动扩大栈空间

 30         s->base = (ElemType *)realloc(s->base, (s->stackSize + STACK_INCREMENT)*sizeof(ElemType));

 31         if(!s->base)

 32             exit(-1);

 33     }

 34     *(s->top) = e;

 35     s->top++;

 36 }

 37 //出栈

 38 void pop(sqStack *s, ElemType *e){

 39     if(s->top == s->base){

 40         return ;

 41     }

 42     *e = *(--(s->top));

 43 }

 44 //求栈数据的个数,由于我们不会对其修改，故此处不需传指针

 45 int  stack_len(sqStack s){

 46     return (s.top - s.base); //返回数据的个数    

 47 }

 48 

 49 int main(void){

 50     sqStack s;

 51     char c;

 52     char d,e;

 53     int i = 0;

 54     

 55     init_stack(&s);

 56 

 57     printf("请按输入中缀表达式，以#作为结束标志：\n\n");

 58     scanf("%c",&c);

 59     while(c != '#'){

 60         while(c >= '0' && c <= '9'){

 61             printf("%c",c);

 62             scanf("%c",&c);

 63             if(c<'0' || c>'9'){

 64                 printf(" ");

 65             }

 66         }

 67         if(')' == c){

 68             pop(&s,&e);

 69             while('(' != e){

 70                 printf("%c ",e);

 71                 pop(&s,&e);

 72             }

 73         }else if( '+' == c|| '-'==c){

 74             if(!stack_len(s)){

 75                 push(&s,c);

 76             }else{

 77                 do{

 78                     pop(&s,&e);

 79                     if('(' == e){

 80                         push(&s,e);

 81                     }else{

 82                         printf("%c ",e);

 83                     }

 84                 }while(stack_len(s) && '(' != e);

 85                 push(&s, c);

 86             }

 87         }else if('*' == c || '/'==c || '('==c){

 88             push(&s,c);

 89         }else if('#' == c){

 90             break;

 91         }else{

 92             printf("请输入正确的中缀表达式!!!\n");

 93             return -1;

 94         }

 95         scanf("%c",&c);

 96     }

 97     while(stack_len(s)) {

 98         pop(&s,&d);        //将最终的计算结果弹出

 99         printf("%c ",d);

100     }

101     printf("\n\n");

102     return 0;

103 }