栈-中缀式转后缀式

最新推荐文章于 2021-04-13 22:10:06 发布

冶无晴

最新推荐文章于 2021-04-13 22:10:06 发布

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CC 4.0 BY-SA版权

文章标签：数据结构

本文链接：https://blog.youkuaiyun.com/sinat_25639129/article/details/51791005

本文介绍了一种使用栈数据结构将中缀表达式转换为后缀表达式的方法。通过定义sqStack结构体来实现栈，并提供初始化、压栈、弹栈等操作。文章展示了完整的C语言代码实现过程，包括输入中缀表达式并将其转换为对应的后缀表达式。

#include "stdafx.h"
#include "malloc.h"
#include "windows.h"
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

#define INIT_SIZE   20
#define INCRESEMENT 10
#define MAXBUFFER   10  
typedef char ElemType;
typedef struct
{
    int stacksize;
    ElemType *base;
    ElemType *top;
}sqStack;

void initStack(sqStack *s)
{
    s->base = (ElemType*)malloc(INIT_SIZE*sizeof(ElemType));
    if(!s->base) exit(0);
    s->top = s->base;
    s->stacksize = INIT_SIZE;
}

void Push(sqStack *s, ElemType e)
{
    if(s->top - s->base >= s->stacksize)
    {
        s->base = (ElemType*)realloc(s->base, (s->stacksize+INCRESEMENT)*sizeof(ElemType));
        if(!s->base) exit(0);
    }
    *(s->top) = e;
    s->top++;
}

void Pop(sqStack*s, ElemType *e)
{
    if(s->base == s->top) return;
    s->top--;
    *e = *(s->top);
}

int StackLen(sqStack s)
{
    return (s.top-s.base);
}

int Priority(sqStack s)
{
    if(s.base == s.top) return 0;
    else
    {
        s.top--;
        switch(*s.top)
        {
        case '+':
        case '-': 
            return 1;
        case '*':
        case '/': 
            return 2;
        case '(': 
            return -1;
        }
    }
}

int decidec( ElemType e)
{
    if(isdigit(e) || e=='.') return 0;
    if(e=='*' || e=='/' || e=='(') return 1;
    if(e==')') return 2;
    else return 3;
}

int main(int argc, char* argv[])
{
    sqStack s;
    initStack(&s);
    printf("输入中缀式（#结束）：\n");
    char c;
    scanf("%c",&c);
    char str[MAXBUFFER];
    ElemType x;
    int i = 0;
    while(c!='#')
    {
        switch(decidec(c))
        {
        case 0:
            while(!decidec(c))
            {
                printf("%c",c);
                scanf("%c",&c);
            }
            printf(" ");
            break;
        case 1:
            Push(&s, c);
            scanf("%c",&c);
            break;
        case 2:
            while(StackLen(s)){
                    Pop(&s, &x);
                    if(x=='(') break;
                    else printf("%c ",x);
                }
            scanf("%c",&c);
            break;
        case 3:
            if(Priority(s)==2)
            {
                while(StackLen(s)){
                    Pop(&s, &x);
                    if(x=='(') break;
                    else printf("%c ",x);
                }
            }
            else Push(&s,c);
            scanf("%c",&c);
            break;
        }
    }
    while(StackLen(s))
    {
        Pop(&s, &x);
        printf("%c ",x);
    }
    printf("\n");
    return 0;
}