棧的基本概念和實現我在上一篇文章中實現了，現在做一下練習，一個簡單的四則運算的實現，還是比較簡單的，我並沒有再往下實現括號的四則運算，這個都是次要的，主要是掌握棧的操作方法，和一些基本的注意事項，其實這個程式碼我之前刪除了又重寫了一邊，第一遍在實現的過程中對自己的程式碼並沒有感到滿意。在這個練習的過程中自己還是學到了很多的細節上的問題，有些東西只有自己動手去做才會明白其中的重要的部分。多多實踐才是提高的方法，部落格就是監督自己的手段之一。

下面上程式碼：

#include <stdio.h>
#include "seqstack.h"
#include <string.h>
#include <stdlib.h>

#define BUF_SIZE 1024

SeqStack stack_number;
SeqStack stack_char;

long char_to_long (char *c , int count) ;
int is_vaild (char *buf , int count) ;
long search_buf (char * buf , int count) ;
long count_res (long m , long n , char op) ;

int main () {
    int count = 0;
    char c;
    char buf[BUF_SIZE];
    long res;

    init_stack (&stack_char);
    init_stack (&stack_number);

    while ((c = getchar()) != '#') {
        if (count == BUF_SIZE - 1) {
            printf ("the buf is full\n");
            break;
        }
        else {
            buf[count] = c;
            count++;
        }
    }
    if (!is_vaild (buf , count)) {
        printf ("the input string error\n");
        return 1;
    }
    res = search_buf(buf , count);
    printf ("the res is %ld\n" , res);
}

long search_buf (char *buf , int count) {
    char *point_arr[BUF_SIZE];
    int i , point_count;
    char temp;
    long op;
    long s , t ;
    char op_arr[BUF_SIZE];
    int op_count = 0;
    long data_arr[BUF_SIZE];
    int data_count = 0;
    int length;
    long res;

    point_arr[0] = buf-1;
    point_count = 1;

    for (i = 0 ; i < count ; i++) {
        temp = *(buf+i);
        if (temp == '*' || temp == '\\' || temp == '+' || temp == '-') {
            point_arr[point_count] = buf+i;
            point_count++;
        }
    }
    point_arr[point_count] = buf+count;
    point_count++;

    for (i = 0 ; i < point_count - 2 ; i++) {
        op_arr[op_count] = *point_arr[i+1];
        op_count++;
    }
    for (i = 0 ; i < point_count - 1 ; i++) {
        length = point_arr[i+1] - (point_arr[i]+1);
        data_arr[data_count] = char_to_long(point_arr[i]+1 , length);
        data_count++;
    }
    //above all the search is ok
    push (&stack_number , data_arr[0]);

    for (i = 0 ; i < op_count ; i++) {
        if (op_arr[i] == '+' || op_arr[i] == '-') {
            push (&stack_char , (long)op_arr[i]);
            push (&stack_number , data_arr[i+1]);
        }else if (op_arr[i] == '*' || op_arr[i] == '\\') {
            pop (&stack_number , &s);
            t = count_res (s , data_arr[i+1] , op_arr[i]);
            push (&stack_number , t);
        } 
    }
    pop (&stack_number , &res);
    while (!is_empty (&stack_char)) {
        pop (&stack_char , &op);
        pop (&stack_number , &s);
        res = count_res (s , res , (char)op);
    }
    return res;
}

int is_vaild (char *buf , int count) {
    int i;
    char temp;
    int flag = 1;

    for (i = 0 ; i < count ; i++) {
        temp = *(buf+i);

        if ((temp >='0' && temp <='9') || temp == '+' || temp == '-' || temp == '*' || temp == '\\')
            continue;
        else {
            flag = 0;
            break;
        }
    }
    return flag;
}

long char_to_long (char *c , int count) {
    int i;
    long res = 0;
    int temp;

    for (i = 0 ; i < count ; i++) {
        if (*(c+i) > '9' || *(c+i) < '0') {
            printf ("the input seq error\n");
            return -1;
        }
        temp = *(c+i) - '0';
        res *= 10;
        res += temp;
    }
    return res;
}

long count_res (long m , long n , char op) {
    long temp;
    switch (op) {
        case '+':
            return m+n;
        case '-':
            return m-n;
        case '*':
            return m*n;
        case '\\':
            return (m/n);
        default:
            return -1;
    }
}