088.批量计算数学题

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int f_calc(int p_v1, char p_sign, int p_v2) {
 switch (p_sign) {
 case '+':
  return p_v1 + p_v2;
 case '-':
  return p_v1 - p_v2;
 case '*':
  return p_v1 * p_v2;
 case '/': //这个地方有一个致命的地方
  if (!p_v2) {
   return -1;
  }
  else {
   return p_v1 / p_v2;
  }
 }
}

void main() {
 FILE* l_fp_read = fopen("1.txt", "r");
 if (!l_fp_read) {
  printf("打开读文件失败!\n");
  system("pause");
  return;
 }

 int l_last_position = NULL;
 char l_read_line[50] = { NULL };
 char l_write_line[50] = { NULL };
 int * p_save = NULL;
 int l_count = NULL;

 while (!feof(l_fp_read)) {
  fgets(l_read_line, sizeof(l_read_line), l_fp_read);
  int l_this_position = ftell(l_fp_read);
  if (l_this_position != l_last_position) {
   l_last_position = l_this_position;
   int l_v1, l_v2;
   char l_sign;
   int l_result;
   sscanf(l_read_line, "%d%c%d=", &l_v1, &l_sign, &l_v2);
   l_result = f_calc(l_v1, l_sign, l_v2);
   sprintf(l_write_line, "%d%c%d=%d\n", l_v1, l_sign, l_v2, l_result);
   //在C语言中,只要是系统内置的函数,如果里面包含scanf这个关键字.
   //你一定要使用取地址符号才能正常使用.
   l_count++;
   p_save = (int *)realloc(p_save, l_count*sizeof(int));
   int l_sizecount = strlen(l_write_line) + 1;
   p_save[l_count - 1] = (int)calloc(l_sizecount, sizeof(char));
   strcpy((char *)p_save[l_count - 1], l_write_line);
  }
 }

 FILE* l_fp_write = fopen("1.txt", "w");
 if (!l_fp_write) {
  printf("打开写文件失败!\n");
  system("pause");
  return;
 }
 for (size_t i = 0; i < l_count; i++) {
  fputs((char *)p_save[i], l_fp_write);//ctrl+J
  free((char *)p_save[i]);
 }

 free(p_save);
 fclose(l_fp_read);
 printf("\n自动答题工作完成\n");
 system("pause");