数据结构课程设计··表达式翻译

#include<stdio.h>

#include<stdlib.h>

#define TRUE 1

#define FALSE 0

#define MAXNUM 100

typedef int DataType;

struct SeqStack

{ DataType s[MAXNUM];

int t;

};

typedef struct SeqStack *PSeqStack;

PSeqStack createEmptyStack_seq()

{

PSeqStack pastack;

pastack = (PSeqStack)malloc(sizeof(struct SeqStack));

if (pastack == NULL)

printf("Out of space!!\n");

else

pastack->t = -1;

return pastack;

} int isEmptyStack_seq(PSeqStack pastack)

{

return pastack->t == -1;

} void push_seq(PSeqStack pastack, DataType x)

{

if (pastack->t >= MAXNUM - 1)

printf("Overflow!\n");

else

{

pastack->t = pastack->t + 1;

pastack->s[pastack->t] = x;

}

} void pop_seq(PSeqStack pastack)

{

if (pastack->t == -1)

printf("Underflow!\n");

else

pastack->t = pastack->t - 1;

} DataType top_seq(PSeqStack pastack)

{

return pastack->s[pastack->t];

} int infixtoSuffix(const char * infix, char * suffix)

{ /*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 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表示刚读入的不是数字字符，

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(); /*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;

} 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 < limit - 1 && (c = getchar()) != EOF && c != '\n')

line[i++] = c;

line[i] = '\0';

} void main()

{ char c, infix[MAXNUM], suffix[MAXNUM];

int result;

int flag = TRUE;

while (flag == TRUE)

{

printf("请输入表达式!\nInput:");

getline(infix, MAXNUM);

if(infixtoSuffix(infix, suffix) == TRUE)

printf("suffix:%s\n", suffix);

else

{

printf("无效的输入!\n");

printf("\nContinue? (y/n)");

scanf("%c", &c);

if (c == 'n' || c == 'N') flag = FALSE;

while (getchar() != '\n');

printf("\n");

continue;

}

if(calculateSuffix(suffix, &result) == TRUE)

printf("Result:%d\n", result);

else

printf("Invalid suffix!\n");

printf("\nContinue? (y/n)");

scanf("%c", &c);

if (c == 'n' || c == 'N') flag = FALSE;

while (getchar() != '\n');

printf("\n");

}

}