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

//中缀表达式转换为后缀表达式(逆波兰表达式)
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <ctype.h>

#define STACK_INIT_SIZE        20    //初始栈大小
#define STACK_INCREMENT        10  //扩充栈时每次增加的内存
#define MAXBUFFER            10  //缓冲区

typedef char ElemType;            //栈中的数据类型
typedef struct {
    ElemType *base;
    ElemType *top;
    int stackSize;
}sqStack;

//初始化栈
void init_stack(sqStack *s){
    s->base = (ElemType *)malloc(STACK_INIT_SIZE * sizeof(ElemType));
    if(!s->base)
        exit(-1);
    s->top = s->base;
    s->stackSize = STACK_INIT_SIZE;
}
//入栈
void push(sqStack *s,ElemType e){
    if(s->top - s->base >= s->stackSize){    //检测栈是否已满
        //若是已满，则自动扩大栈空间
        s->base = (ElemType *)realloc(s->base, (s->stackSize + STACK_INCREMENT)*sizeof(ElemType));
        if(!s->base)
            exit(-1);
    }
    *(s->top) = e;
    s->top++;
}
//出栈
void pop(sqStack *s, ElemType *e){
    if(s->top == s->base){
        return ;
    }
    *e = *(--(s->top));
}
//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
int  stack_len(sqStack s){
    return (s.top - s.base); //返回数据的个数    
}

int main(void){
    sqStack s;
    char c;
    char d,e;
    int i = 0;
    
    init_stack(&s);

    printf("请按输入中缀表达式，以#作为结束标志：

");
    scanf("%c",&c);
    while(c != '#'){
        while(c >= '0' && c <= '9'){
            printf("%c",c);
            scanf("%c",&c);
            if(c<'0' || c>'9'){
                printf(" ");
            }
        }
        if(')' == c){
            pop(&s,&e);
            while('(' != e){
                printf("%c ",e);
                pop(&s,&e);
            }
        }else if( '+' == c|| '-'==c){
            if(!stack_len(s)){
                push(&s,c);
            }else{
                do{
                    pop(&s,&e);
                    if('(' == e){
                        push(&s,e);
                    }else{
                        printf("%c ",e);
                    }
                }while(stack_len(s) && '(' != e);
                push(&s, c);
            }
        }else if('*' == c || '/'==c || '('==c){
            push(&s,c);
        }else if('#' == c){
            break;
        }else{
            printf("请输入正确的中缀表达式!!!
");
            return -1;
        }
        scanf("%c",&c);
    }
    while(stack_len(s)) {
        pop(&s,&d);        //将最终的计算结果弹出
        printf("%c ",d);
    }
    printf("

");
    return 0;
}