C语言 将用户输入值分配给分配的内存

Question

该程序背后的想法是声明学生信息的数据结构，然后让用户将信息输入到输入的学生数量的数据结构的每个字段中。我的问题是当我输入名字时程序停止工作。怎么了？谢谢你的时间。

//Inclusion of necessary header files
#include <stdio.h>
#include <stdlib.h>
//Data structure declaration
struct student{
char firstName[20];
char lastName[20];
char id[10];
char gender;
int age;
double gpa;
};
//Function prototypes
void readStudentsInformation(struct student *, int size); 
void outputStudents(struct student *, int size);
double averageGPA(struct student *, int size);
void sortByLastName(struct student *, int size);
void sortByGPA(struct student *, int size);

//Entry point
int main()
{
    //Variable delcaration
    int size;
    struct student *ptr;
    //Input prompt and function
    printf("How many students?n");
    scanf_s("%d", &size);
    //Allocation memory for struct student times the number of students and assigning it to a struct student pointer for external function modification
    ptr = (struct student*)malloc(sizeof(struct student)*size);
    //readStudentsInformation Function call
    readStudentsInformation(ptr, size);
    //Exit sequence
    return 0;
}
//This functions reads the information for all the students from the keyboard, taking the class size through the pointer method and struct student from main
void readStudentsInformation(struct student *ptr, int size) 
{
    //For loop controller declaration
    int i;
    //Function message
    printf("Student Information Formn");
    //This for loop increments the "index" of each students info location where user input is stored
    for(i=0;i<size;i++)
    {
        //Each field has it's appropriate input limit
        printf("Please enter Student %d's First Name(20 characters).n", i+1);
        scanf_s("%20s", ptr[i].firstName);
        printf("Please enter Student %d's Last Name(20 characters).n", i+1);       
        scanf_s("%20s", ptr[i].lastName);                                   
        printf("Please enter Student %d's ID(10 characters).n",i+1);               
        scanf_s("%10s", ptr[i].id);
        printf("Please enter Student %d's gender(M/F).n",i+1);
        scanf_s("%c", ptr[i].gender);
        printf("Please enter Student %d's age.n",i+1);
        scanf_s("%3d", ptr[i].age);   //Only 3 digits can be put in at a time
        printf("Please enter Student %d's GPA.n", i+1);
        scanf_s("%.1lf", ptr[i].gpa);   //From the lab it can be seen that no more than one decimal place is featured, so the same is done here
    }
    //Exit to main
    return;
}

Answer 1

你应该这样做

scanf_s("%20s", ptr[i].firstName);

阅读名字。 ptr+i会给你student结构。您希望在结构成员中存储数据。

为此也更改您的其他scanf。

Answer 2

您可以使用

scanf("%s",ptr[i].firstName);

对于 scanf（） 中的其余结构成员，依此类推。

Answer 3

将

scanf_s更改为scanf并更改此块，如下所示：

    scanf("%c", &ptr[i].gender);
    printf("Please enter Student %d's age.n",i+1);
    scanf("%3d", &ptr[i].age);   //Only 3 digits can be put in at a time
    printf("Please enter Student %d's GPA.n", i+1);
    scanf("%1lf", &ptr[i].gpa);