101 - 102 課堂代碼

``` C

#include <stdio.h>

#include <stdlib.h>

#include <ctype.h>

#include <string.h>

#include "sqstack.h"

static void compute(sqstack *snum, datatype *op) {

datatype n1, n2, n;

st_pop(snum, &n2);

st_pop(snum, &n1);

switch(*op) {

case '+':

n = n1 + n2;

break;

case '-':

n = n1 - n2;

break;

case '*':

n = n1 * n2;

break;

case '/':

n = n1 / n2;

break;

default:

exit(1);

}

st_push(snum, &n);

}

void deal_bracket(sqstack *snum, sqstack *sop) {

datatype old_op;

st_top(sop, &old_op);

while(old_op != '(') {

st_pop(sop, &old_op);

compute(snum, &old_op);

st_top(sop, &old_op);

}

st_pop(sop, &old_op);

}

static int get_pri(int op) {

switch(op) {

case '(':

return 0;

case '+':

case '-':

return 1;

case '*':

case '/':

return 2;

}

}

void deal_op(sqstack *snum, sqstack *sop, int op) {

datatype old_op;

if(st_isempty(sop) || op == '(') {

st_push(sop, &op);

return;

}

st_top(sop, &old_op);

if(get_pri(op) > get_pri(old_op)) {

st_push(sop, &op);

return;

}

while(get_pri(op) <= get_pri(old_op)) {

st_pop(sop, &old_op);

compute(snum, &old_op);

if(st_isempty(sop))

break;

st_top(sop, &old_op);

}

st_push(sop, &op);

}

int main() {

int i = 0;

char str[] = "(11+3)*2-5";

sqstack *snum, *sop;

int value = 0;

int flag = 0;

snum = st_create();

if(snum == NULL)

exit(1);

sop = st_create();

if(sop == NULL)?

exit(1);

while(str[i] != '\0') {

if(isdigit(str[i])) {

value = value * 10 + str[i] - '0';

flag = 1;

} else {

if(flag) {

st_push(snum, &value);

flag = 0;

value = 0;

}

if(str[i] == ')') {

deal_bracket(snum, sop);

} else {

deal_op(snum, sop, str[i]);

}

}

i++;

}

if(flag)

st_push(snum, &value);

int old_op;

while(!st_isempty(sop)) {

st_pop(sop, &old_op);

compute(snum, &old_op);

st_top(sop, &old_op);

}

int res;

st_top(snum, &res);

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

st_destory(snum);

st_destory(sop);

exit(0);

}

```