scanf() 的问题

Question

我正在使用一个程序（非常简单），它需要用户使用 scanf 进行输入。这些值存储在结构数组中。无论如何，我认为我的所有语法都正确（如果我不纠正我的话），但是每当我想 printf 查看结果时，我都没有从 ID[i].Middle_Name 获得值。由于我不明白的原因，它似乎是空的。我试图添加一个打印语句来尝试调试它，但仍然没有。也许我错过了什么？

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <stdarg.h>

struct Students{
  char First_Name[20];
  char Last_Name[20];
  char Middle_Name[20];
  int Age;
};

int main(void){
    int n = 0;  //number of students
    int i = 0;      //counter

  printf("Please enter the total number of students in your class: ");
  scanf("%d", &n);
  struct Students ID[n];
  printf("\n");

  printf("******************** \n");
  printf("After entering student info, they are displayed in full_name/middle_name/age order. \n");
  printf("******************** \n");

  for(i = 1; i <= n; i++){
      printf("Please enter the first name of student with  ID: %d \t", i);
      scanf("%s", (ID[i].First_Name));
      printf("\n");

      printf("Please enter the last name of student with ID: %d \t", i);
      scanf("%s", (ID[i].Last_Name));
      printf("\n");

      printf("Please enter the middle name of student ID: %d \t", i);
      scanf("%s", (ID[i].Middle_Name)); 
      printf("\n");

      printf("Please enter the age of student ID: %d \t", i);
      scanf("%d", &(ID[i].Age));
      printf("\n");

  }
  printf("In your class, we have: \n");
  printf("%s", ID[1].Middle_Name);

  for(i = 1; i <= n; i++){
      printf("%s \t", ID[i].First_Name); 
      printf("%s \t", ID[i].Last_Name); 
      printf("%s \t", ID[i].Middle_Name); 
      printf("%d \n", ID[i].Age); 
  }
  return(0);
}

Answer 1

您必须以i = 0 而不是i = 1 开头才能获取数组的第一个元素。您应该将i <= n 替换为i < n。

for(i = 0; i < n; i++)
{
    ...
}

Answer 2

我建议将 scanf ("%s", id[i]. ...) 替换为 gets 例如。

gets(ID[i].Middle_Name);

并且在循环中也从 0 开始，而不是 1

for(i = 0; i

Answer 3

for(i = 0; i <= n; i++)
{

//Your input code

}

for(i = 0; i <= n; i++)
{

      // your output code

}

Answer 4

您的代码中有错误的语法

struct Students ID[n]; 

数组长度必须是一个常量，或者你可以像这样使用new

struct Students *ID = new struct Students[n];

Answer 5

// <-- note leading ' ' on all format strings
// <-- always check returned value from input statements
// <-- following line would try to access past end of array, 
//     arrays start with offset of 0,
//     for(i = 1; i <= n; i++)

#include <stdio.h>
#include <stdlib.h>
//#include <string.h>
//#include <stdarg.h>

struct Students
{
  char First_Name[20];
  char Last_Name[20];
  char Middle_Name[20];
  int Age;
};

int main(void){
    int n = 0;  //number of students
    int i = 0;      //counter

  printf("Please enter the total number of students in your class: ");
  if( 1 != scanf(" %d", &n) )
  {
      perror( "scanf failed reading num students" );
      exit( EXIT_FAILURE );
  }

  struct Students ID[n];
  printf("\n");

  printf("******************** \n");
  printf("After entering student info, they are displayed in full_name/middle_name/age order. \n");
  printf("******************** \n\n");


  for( i=0; i< n; i++ )
  {
      printf("Please enter the first name of student with  ID: %d \t", i+1);
      if( 1 != scanf(" %s", (ID[i].First_Name)) )
      {
          perror( "scanf failed for first name" );
          exit( EXIT_FAILURE );
      }

      printf("\n");

      printf("Please enter the last name of student with ID: %d \t", i+1);
      if( 1 != scanf(" %s", (ID[i].Last_Name)) ) // <-- check returned value
      {
          perror( "scanf failed for last name" );
          exit( EXIT_FAILURE );
      }

      printf("\n");

      printf("Please enter the middle name of student ID: %d \t", i+1);
      if( 1 != scanf(" %s", (ID[i].Middle_Name)) ) // <-- check returned value
      {
          perror( "scanf failed for middle name" );
          exit( EXIT_FAILURE );
      }

      printf("\n");

      printf("Please enter the age of student ID: %d \t", i+1);
      if( 1 != scanf(" %d", &(ID[i].Age)) ) // <-- check returned value 
      {
          perror( "scanf failed for student age" );
          exit( EXIT_FAILURE );
      }

      printf("\n");
  } // end while

  printf("In your class, we have: \n");
  printf("%s", ID[1].Middle_Name);

  // <-- following line would try to access past end of array, arrays start with offset of 0, not 1
  //for(i = 1; i <= n; i++)
  for( i=0; i<n; i++ )
  {
      printf("%s \t", ID[i].First_Name);
      printf("%s \t", ID[i].Last_Name);
      printf("%s \t", ID[i].Middle_Name);
      printf("%d \n", ID[i].Age);
      printf("\n"); // put each student on a new line
  } // end for
  return(0);
}