用堆栈实现将中缀表达式转化为后缀表达式

用堆栈实现将中缀表达式转化为后缀表达式
用堆栈实现将中缀表达式转化为后缀表达式

用堆栈实现将中缀表达式转化为后缀表达式
#include
#include
#define TRUE 1
#define FALSE 0
#define MAXNUM 100
typedef int DataType;
typedef struct
{
DataType s[MAXNUM];
int t;
}SeqStack,*PSeqStack;
//构造一个空栈
PSeqStack createEmptyStack_seq()
{
PSeqStack pastack;
pastack=(SeqStack*)malloc(sizeof( SeqStack));

if (pastack==NULL)
{
printf("空间不够!\n");
}
else
{
pastack->t=-1;
}
return pastack;//返回空栈顶
}
//清空栈
int isEmptyStack_seq(PSeqStack pastack)
{
return pastack->t==-1;
}
//入栈
void push_seq(PSeqStack pastack, DataType x)
{
if (pastack->t >= MAXNUM - 1)
printf("上溢!\n");
else
{
pastack->t = pastack->t+1;
pastack->s[pastack->t]=x;
}
}
//出栈
void pop_seq(PSeqStack pastack)
{
if (pastack->t==-1)
{
printf("下溢!\n");
}
else
{
pastack->t = pastack->t-1;
}
}
//返回栈顶元素的值
DataType top_seq(PSeqStack pastack)
{
return pastack->s[pastack->t];
}
/*将中缀表达式转换为后缀表达式,顺利转换返回true,若转换过程中发现中缀表达式非法则返回false*/
int infixtoSuffix(const char* infix, char* suffix)
{
int state_int = FALSE; /*state_int记录状态,等于true表示刚读入的是数字字符,等于false表示刚读入的是运算符,
设置这个变量是为了在每输出一个整数后输出一个空格,以免连续输出的两个整数混在一起.*/
char c, c2;
PSeqStack ps = createEmptyStack_seq(); /*构造一个运算符栈*/
int i, j = 0;
if(infix[0]=='\0')
{
return FALSE; /*不允许出现空表达式*/
}
for(i=0; infix[i]!='\0';i++)
{
c=infix[i];
switch(c)
{
case ' ':
case '\t':
case '\n':
if(state_int== TRUE)
{
suffix[j++]=' ';/*状态从true转换为false时输出一个空格*/
}
state_int= FALSE;
break; /*遇到空格或制表符忽略*/
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
state_int =TRUE;
suffix[j++]=c; /*遇到数字输出*/
break;
case '(':
if(state_int==TRUE)
{
suffix[j++]=' ';/*状态从true转换为false时输出一个空格*/
}
state_int=FALSE;
push_seq(ps, c); /*遇到左括号,入栈*/
break;
case ')':
if(state_int== TRUE)
{
suffix[j++]=' ';/*状态从true转换为false时输出一个空格*/
}
state_int=FALSE;
c2 = ')';
while(!isEmptyStack_seq(ps))
{
c2=top_seq(ps);/*取栈顶*/
pop_seq(ps); /*出栈*/
if(c2 =='(')
{
break;
}
suffix[j++]=c2;
}
if(c2 !='(')
{
free(ps);
suffix[j++]='\0';
return FALSE;
}
break;
case '+':
case '-':
if(state_int == TRUE)
{
suffix[j++] = ' ';
}
state_int = FALSE;
while(!isEmptyStack_seq(ps))
{
c2 = top_seq(ps);
if(c2 =='+'|| c2 =='-'|| c2 == '*' || c2 == '/')
{
pop_seq(ps);
suffix[j++] = c2;
}
else if(c2=='(')
{
break;
}
}
push_seq(ps, c);
break;
case '*':
case '/':
if(state_int==TRUE)
{
suffix[j++] = ' ';
}
state_int = FALSE;
while(!isEmptyStack_seq(ps))
{
c2 = top_seq(ps);
if(c2 == '*' || c2 == '/')
{
pop_seq(ps);
suffix[j++] = c2;
}
else if(c2=='+'||c2=='-'||c2=='(')
{
break;
}
}
push_seq(ps, c);
break;
default:
free(ps);
suffix[j++] = '\0';
return FALSE;
}
}
if(state_int == TRUE)
{
suffix[j++] = ' ';
}
while(!isEmptyStack_seq(ps))
{
c2 = top_seq(ps);
pop_seq(ps);
if(c2 == '(')
{
free(ps);
suffix[j++] = '\0';
return FALSE;
}
suffix[j++] = c2;
}
free(ps);
suffix[j++] = '\0';
return TRUE;
}
//计算后缀
int calculateSuffix(const char * suffix, int * presult)
{
int state_int = FALSE;
PSeqStack ps = createEmptyStack_seq();
int num = 0, num1, num2;
int i;
char c;
for(i = 0; suffix[i] != '\0'; i++)
{
c = suffix[i];
switch(c)
{
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
if(state_int == TRUE)
{
num = num * 10 + c - '0';
}
else
{
num = c - '0';
}
state_int = TRUE;
break;
case ' ':
case'\t':
case '\n':
if (state_int == TRUE)
{
push_seq(ps, num);
state_int = FALSE;
}
break;
case '+':
case '-':
case '*':
case '/':
if(state_int == TRUE)
{
push_seq(ps, num);
state_int = FALSE;
}
if(isEmptyStack_seq(ps))
{
free(ps);
return FALSE;
}
num2 = top_seq(ps);
pop_seq(ps);
if(isEmptyStack_seq(ps))
{
free(ps);
return FALSE;
}
num1 = top_seq(ps);
pop_seq(ps);
if(c == '+')
{
push_seq(ps, num1 + num2);
}
if(c == '-')
{
push_seq(ps, num1 - num2);
}
if(c == '*')
{
push_seq(ps, num1 * num2);
}
if(c == '/')
{
push_seq(ps, num1 / num2);
}
break;
default:
free(ps);
return FALSE;
}
}
*presult = top_seq(ps);
pop_seq(ps);
if(!isEmptyStack_seq(ps))
{
free(ps);
return FALSE;
}
free(ps);
return TRUE;
}
void getline(char* line, int limit)
{
char c;
int i=0;
while(i