我是用的是VS2019
错误是 使用了可能未初始化的本地指针变量fp
指针乱指，应该怎样修改呢
以下是我的代码：
#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>
#include<string.h>
struct student1//学生信息结构体
{
char name[10];//姓名
int num;//学号
int grade[4];//语文 数学 英语
};
struct student2//单链表节点定义
{
struct student1 data;//单链表数据域，用于存储学生信息。
struct student2 *next;//指针域
};
/* struct student3
{
char name[10];//姓名
int num;//学号
int grade[4];//语文 数学 英语
};
struct student4//单链表节点定义
{
struct student3 data1;//单链表数据域，用于存储学生信息。
struct student3 data2;//指针域
};*/
struct student2 *creat(struct student2 *head)//建立单链表，输入学生信息
{
struct student2 *p1, *p2;
int a = 0, b = 1, c;
char str1[15] = { "studenta.txt" };
char str2[15] = { "studentb.txt" };
char ch = ' ';
FILE *fp;
p1 = p2 = (struct student2*)malloc(sizeof(struct student2));//申请空间
while (a <= 0)
{
printf("请输入您要输入的学生人数：");
scanf("%d", &a);
if (a <= 0)
printf("输入有误，请重新输入！\n");
}
printf("1.studenta.txt文件\n2.studentb.txt\n");
printf("请选择您要保存的文件：");
scanf("%d", &c);
{
if (c == 1)
fp = fopen(str1, "w+");
else if (c == 2)
fp = fopen(str2, "w+");
}
printf("请输入第%d学生的姓名：", b);
scanf("%s", &(p1->data.name));
fputs((p1->data.name), fp);//将字符串读入文件
fputc(ch, fp);//向文件写入一个空格字符
printf("请输入第%d个学生的学号：", b);
scanf("%d", &(p1->data.num));
fprintf(fp, "%d", (p1->data.num));
fputc(ch, fp);
printf("请输入第%d学生的语文成绩：", b);
scanf("%d", &(p1->data.grade[0]));
fprintf(fp, "%d", (p1->data.grade[0]));
fputc(ch, fp);
printf("请输入第%d学生的数学成绩：", b);
scanf("%d", &(p1->data.grade[1]));
fprintf(fp, "%d", (p1->data.grade[1]));
fputc(ch, fp);
printf("请输入第%d学生的英语成绩：", b);
scanf("%d", &(p1->data.grade[2]));
fprintf(fp, "%d", (p1->data.grade[2]));
fputc(ch, fp);
(p1->data.grade[3]) = ((p1->data.grade[0]) + (p1->data.grade[1]) + (p1->data.grade[2]));
fprintf(fp, "%d", (p1->data.grade[3]));
fprintf(fp, "\n");
printf("%s的总成绩为：%d\n", (p1->data.name), (p1->data.grade[3]));
b++;
p1->next = NULL;
while (b <= (a + 1))
{
if (head == NULL)
head = p1;/*空表，接入表头*/
else
p2->next = p1;/*非空表，接到表尾*/
p2 = p1;
if (b != a + 1)
{
p1 = (struct student2*)malloc(sizeof(struct student2));
printf("请输入第%d学生的姓名：", b);
scanf("%s", &(p1->data.name));
fputs((p1->data.name), fp);//将字符串读入文件
fputc(ch, fp);//向文件写入一个空格
printf("请输入第%d个学生的学号：", b);
scanf("%d", &(p1->data.num));
fprintf(fp, "%d", (p1->data.num));
fputc(ch, fp);
printf("请输入第%d学生的语文成绩：", b);
scanf("%d", &(p1->data.grade[0]));
fprintf(fp, "%d", (p1->data.grade[0]));
fputc(ch, fp);
printf("请输入第%d学生的数学成绩：", b);
scanf("%d", &(p1->data.grade[1]));
fprintf(fp, "%d", (p1->data.grade[1]));
fputc(ch, fp);
printf("请输入第%d学生的英语成绩：", b);
scanf("%d", &(p1->data.grade[2]));
fprintf(fp, "%d", (p1->data.grade[2]));
fputc(ch, fp);
(p1->data.grade[3]) = ((p1->data.grade[0]) + (p1->data.grade[1]) + (p1->data.grade[2]));
fprintf(fp, "%d", (p1->data.grade[3]));
fprintf(fp, "\n");
printf("%s的总成绩为：%d\n", (p1->data.name), (p1->data.grade[3]));
p1->next = NULL;
b++;
}
else break;
}
fclose(fp);
return head;
}
void printLinkList(struct student2 *head)//输出学生信息
{
struct student2 *temp;
temp = head;//取得链表的头指针
printf("姓名 学号 语文 数学 英语 总分\n");
while (temp != NULL)//只要是非空表
{
printf("%s %d %d %d %d %d \n", (temp->data.name), (temp->data.num), (temp->data.grade[0]), (temp->data.grade[1]), (temp->data.grade[2]), (temp->data.grade[3]));//输出链表节点的值
temp = temp->next;///跟踪链表增长
}
}
void find(struct student2 *head)
{
int b;
struct student2 *p;
printf("请输入您要查找的学生的学号：");
scanf("%d", &b);
p = head;
while (p != NULL)
{
if (b == p->data.num)
{
printf("%s %d %d %d %d %d \n", (p->data.name), (p->data.num), (p->data.grade[0]), (p->data.grade[1]), (p->data.grade[2]), (p->data.grade[3]));//输出链表节点的值
break;
}
else
p = p->next;
}
}
void display(struct student2 *head)
{
struct student2 *temp;
FILE *fp;
char ch = ' ';
fp = fopen("student4.txt", "w+");
temp = head;//取得链表的头指针
printf("姓名 学号 语文 数学 英语 总分\n");
while (temp != NULL)//只要是非空表
{
if (((temp->data.grade[0])<60) || ((temp->data.grade[1])<60) || ((temp->data.grade[2])<60))
{
printf("%s %d %d %d %d %d \n", (temp->data.name), (temp->data.num), (temp->data.grade[0]), (temp->data.grade[1]), (temp->data.grade[2]), (temp->data.grade[3]));//输出链表节点的值
fputs((temp->data.name), fp);//将字符串读入文件
fputc(ch, fp);//向文件写入一个空格
fprintf(fp, "%d", (temp->data.num));
fputc(ch, fp);
fprintf(fp, "%d", (temp->data.grade[0]));
fputc(ch, fp);
fprintf(fp, "%d", (temp->data.grade[1]));
fputc(ch, fp);
fprintf(fp, "%d", (temp->data.grade[2]));
fputc(ch, fp);
fprintf(fp, "%d", (temp->data.grade[3]));
fputc(ch, fp);
}
temp = temp->next;
}
fclose(fp);
}
void merge(struct student2 *head)
{
char a, b;
FILE *fpA = fopen("studenta.txt ", "r "); //A文件
FILE *fpB = fopen("studentb.txt ", "r "); //B文件，两个作为输入文件，内容有序
FILE *fpout = fopen("studnetc.txt ", "w "); //输出文件，三个文件都在当前目录下
a = fgetc(fpA);
b = fgetc(fpB);
while (a != EOF && b != EOF) //循环读取并根据比较结果写文件，之后读取新的数据
{
if (a <b) //假设是升序，如果是降序使用 > 即可
{
fputc(a, fpout);
a = fgetc(fpA);
}
else
{
fputc(b, fpout);
b = fgetc(fpB);
}
}
while (a != EOF) //继续读取没有操作的数据
{
fputc(a, fpout);
a = fgetc(fpA);
}
while (b != EOF)
{
fputc(b, fpout);
b = fgetc(fpB);
}
fclose(fpA);
fclose(fpB);
fclose(fpout);
printf("合并成功，请在studentc文件中查看！\n");
}
void sort(struct student2 *head)
{
struct student2 *newNode = (struct student2*)malloc(sizeof(struct student2));
newNode->next = NULL;
while (head)
{
struct student2 *current = head;
struct student2 *pre = head;
struct student2 *preMin = head;
struct student2 *min = head;
while (current)
{
if (current->data.grade[3] < min->data.grade[3])
{
preMin = pre;
min = current;
}
pre = current;
current = current->next;
}
if (min == head)
{
head = head->next;
min->next = newNode->next;
newNode->next = min;
}
else
{
preMin->next = min->next;
min->next = newNode->next;
newNode->next = min;
}
}
head = newNode->next;
free(newNode);
newNode = head;
while (newNode)
{
printf("%s %d %d %d %d %d\n",newNode->data.name,newNode->data.num,newNode->data.grade[0],newNode->data.grade[1],newNode->data.grade[2],newNode->data.grade[3]);
newNode = newNode->next;
}
}
void main()
{
int i = 0;
struct student2 *head = NULL;
struct student2 *creat();
void printLinkList();
printf(" -------------------------------------------------\n");
printf("| ***欢迎使用西安工程大学学生成绩管理系统*** |\n");
printf("| |\n");
printf("| 1.建立学生成绩单 |\n");
printf("| 2.显示学生成绩单 |\n");
printf("| 3.查找学生成绩 |\n");
printf("| 4.按总成绩进行排序并显示 |\n");
printf("| 5.显示需要补考的学生信息并存入新文件4 |\n");
printf("| 6.合并学生成绩单1和2存入新的成绩单3中 |\n");
printf("| 7.退出系统 |\n");
printf("| |\n");
printf(" -------------------------------------------------\n");
while (i != 6)
{
printf("请选择您需要的操作：");
scanf("%d", &i);
if (i <= 0 || i>6)
printf("输入有误，请重新输入！\n");
else if (i == 1)
{
head = NULL;
head = creat(head);
}
else if (i == 2)
printLinkList(head);
else if (i == 3)
find(head);
else if (i == 4)
sort(head);
else if (i == 5)
display(head);
else if (i == 6)
merge(head);
else
printf("退出系统成功！！！\n");
}
}
#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>
#include<string.h>
struct student1//学生信息结构体
{
char name[10];//姓名
int num;//学号
int grade[4];//语文 数学 英语
};
struct student2//单链表节点定义
{
struct student1 data;//单链表数据域，用于存储学生信息。
struct student2* next;//指针域
};
/* struct student3
{
char name[10];//姓名
int num;//学号
int grade[4];//语文 数学 英语
};
struct student4//单链表节点定义
{
struct student3 data1;//单链表数据域，用于存储学生信息。
struct student3 data2;//指针域
};*/
struct student2* creat(struct student2* head)//建立单链表，输入学生信息
{
struct student2* p1, * p2;
int a = 0, b = 1, c;
char str1[15] = { "studenta.txt" };
char str2[15] = { "studentb.txt" };
char ch = ' ';
FILE* fp;
p1 = p2 = (struct student2*)malloc(sizeof(struct student2));//申请空间
while (a <= 0)
{
printf("请输入您要输入的学生人数：");
scanf("%d", &a);
if (a <= 0)
printf("输入有误，请重新输入！\n");
}
printf("1.studenta.txt文件\n2.studentb.txt\n");
printf("请选择您要保存的文件：");
scanf("%d", &c);
if (c == 1)
fp = fopen(str1, "w+");
else
fp = fopen(str2, "w+");
printf("请输入第%d学生的姓名：", b);
scanf("%s", &(p1->data.name));
fputs((p1->data.name), fp);//将字符串读入文件
fputc(ch, fp);//向文件写入一个空格字符
printf("请输入第%d个学生的学号：", b);
scanf("%d", &(p1->data.num));
fprintf(fp, "%d", (p1->data.num));
fputc(ch, fp);
printf("请输入第%d学生的语文成绩：", b);
scanf("%d", &(p1->data.grade[0]));
fprintf(fp, "%d", (p1->data.grade[0]));
fputc(ch, fp);
printf("请输入第%d学生的数学成绩：", b);
scanf("%d", &(p1->data.grade[1]));
fprintf(fp, "%d", (p1->data.grade[1]));
fputc(ch, fp);
printf("请输入第%d学生的英语成绩：", b);
scanf("%d", &(p1->data.grade[2]));
fprintf(fp, "%d", (p1->data.grade[2]));
fputc(ch, fp);
(p1->data.grade[3]) = ((p1->data.grade[0]) + (p1->data.grade[1]) + (p1->data.grade[2]));
fprintf(fp, "%d", (p1->data.grade[3]));
fprintf(fp, "\n");
printf("%s的总成绩为：%d\n", (p1->data.name), (p1->data.grade[3]));
b++;
p1->next = NULL;
while (b <= (a + 1))
{
if (head == NULL)
head = p1;/*空表，接入表头*/
else
p2->next = p1;/*非空表，接到表尾*/
p2 = p1;
if (b != a + 1)
{
p1 = (struct student2*)malloc(sizeof(struct student2));
printf("请输入第%d学生的姓名：", b);
scanf("%s", &(p1->data.name));
fputs((p1->data.name), fp);//将字符串读入文件
fputc(ch, fp);//向文件写入一个空格
printf("请输入第%d个学生的学号：", b);
scanf("%d", &(p1->data.num));
fprintf(fp, "%d", (p1->data.num));
fputc(ch, fp);
printf("请输入第%d学生的语文成绩：", b);
scanf("%d", &(p1->data.grade[0]));
fprintf(fp, "%d", (p1->data.grade[0]));
fputc(ch, fp);
printf("请输入第%d学生的数学成绩：", b);
scanf("%d", &(p1->data.grade[1]));
fprintf(fp, "%d", (p1->data.grade[1]));
fputc(ch, fp);
printf("请输入第%d学生的英语成绩：", b);
scanf("%d", &(p1->data.grade[2]));
fprintf(fp, "%d", (p1->data.grade[2]));
fputc(ch, fp);
(p1->data.grade[3]) = ((p1->data.grade[0]) + (p1->data.grade[1]) + (p1->data.grade[2]));
fprintf(fp, "%d", (p1->data.grade[3]));
fprintf(fp, "\n");
printf("%s的总成绩为：%d\n", (p1->data.name), (p1->data.grade[3]));
p1->next = NULL;
b++;
}
else break;
}
fclose(fp);
return head;
}
void printLinkList(struct student2* head)//输出学生信息
{
struct student2* temp;
temp = head;//取得链表的头指针
printf("姓名 学号 语文 数学 英语 总分\n");
while (temp != NULL)//只要是非空表
{
printf("%s %d %d %d %d %d \n", (temp->data.name), (temp->data.num), (temp->data.grade[0]), (temp->data.grade[1]), (temp->data.grade[2]), (temp->data.grade[3]));//输出链表节点的值
temp = temp->next;///跟踪链表增长
}
}
void find(struct student2* head)
{
int b;
struct student2* p;
printf("请输入您要查找的学生的学号：");
scanf("%d", &b);
p = head;
while (p != NULL)
{
if (b == p->data.num)
{
printf("%s %d %d %d %d %d \n", (p->data.name), (p->data.num), (p->data.grade[0]), (p->data.grade[1]), (p->data.grade[2]), (p->data.grade[3]));//输出链表节点的值
break;
}
else
p = p->next;
}
}
void display(struct student2* head)
{
struct student2* temp;
FILE* fp;
char ch = ' ';
fp = fopen("student4.txt", "w+");
temp = head;//取得链表的头指针
printf("姓名 学号 语文 数学 英语 总分\n");
while (temp != NULL)//只要是非空表
{
if (((temp->data.grade[0]) < 60) || ((temp->data.grade[1]) < 60) || ((temp->data.grade[2]) < 60))
{
printf("%s %d %d %d %d %d \n", (temp->data.name), (temp->data.num), (temp->data.grade[0]), (temp->data.grade[1]), (temp->data.grade[2]), (temp->data.grade[3]));//输出链表节点的值
fputs((temp->data.name), fp);//将字符串读入文件
fputc(ch, fp);//向文件写入一个空格
fprintf(fp, "%d", (temp->data.num));
fputc(ch, fp);
fprintf(fp, "%d", (temp->data.grade[0]));
fputc(ch, fp);
fprintf(fp, "%d", (temp->data.grade[1]));
fputc(ch, fp);
fprintf(fp, "%d", (temp->data.grade[2]));
fputc(ch, fp);
fprintf(fp, "%d", (temp->data.grade[3]));
fputc(ch, fp);
}
temp = temp->next;
}
fclose(fp);
}
void merge(struct student2* head)
{
char a, b;
FILE* fpA = fopen("studenta.txt ", "r "); //A文件
FILE* fpB = fopen("studentb.txt ", "r "); //B文件，两个作为输入文件，内容有序
FILE* fpout = fopen("studnetc.txt ", "w "); //输出文件，三个文件都在当前目录下
a = fgetc(fpA);
b = fgetc(fpB);
while (a != EOF && b != EOF) //循环读取并根据比较结果写文件，之后读取新的数据
{
if (a < b) //假设是升序，如果是降序使用 > 即可
{
fputc(a, fpout);
a = fgetc(fpA);
}
else
{
fputc(b, fpout);
b = fgetc(fpB);
}
}
while (a != EOF) //继续读取没有操作的数据
{
fputc(a, fpout);
a = fgetc(fpA);
}
while (b != EOF)
{
fputc(b, fpout);
b = fgetc(fpB);
}
fclose(fpA);
fclose(fpB);
fclose(fpout);
printf("合并成功，请在studentc文件中查看！\n");
}
void sort(struct student2* head)
{
struct student2* newNode = (struct student2*)malloc(sizeof(struct student2));
newNode->next = NULL;
while (head)
{
struct student2* current = head;
struct student2* pre = head;
struct student2* preMin = head;
struct student2* min = head;
while (current)
{
if (current->data.grade[3] < min->data.grade[3])
{
preMin = pre;
min = current;
}
pre = current;
current = current->next;
}
if (min == head)
{
head = head->next;
min->next = newNode->next;
newNode->next = min;
}
else
{
preMin->next = min->next;
min->next = newNode->next;
newNode->next = min;
}
}
head = newNode->next;
free(newNode);
newNode = head;
while (newNode)
{
printf("%s %d %d %d %d %d\n", newNode->data.name, newNode->data.num, newNode->data.grade[0], newNode->data.grade[1], newNode->data.grade[2], newNode->data.grade[3]);
newNode = newNode->next;
}
}
void main()
{
int i = 0;
struct student2* head = NULL;
//struct student2* creat();
//void printLinkList();
printf(" -------------------------------------------------\n");
printf("| ***欢迎使用西安工程大学学生成绩管理系统*** |\n");
printf("| |\n");
printf("| 1.建立学生成绩单 |\n");
printf("| 2.显示学生成绩单 |\n");
printf("| 3.查找学生成绩 |\n");
printf("| 4.按总成绩进行排序并显示 |\n");
printf("| 5.显示需要补考的学生信息并存入新文件4 |\n");
printf("| 6.合并学生成绩单1和2存入新的成绩单3中 |\n");
printf("| 7.退出系统 |\n");
printf("| |\n");
printf(" -------------------------------------------------\n");
while (i != 6)
{
printf("请选择您需要的操作：");
scanf("%d", &i);
if (i <= 0 || i > 6)
printf("输入有误，请重新输入！\n");
else if (i == 1)
{
head = NULL;
head = creat(head);
}
else if (i == 2)
printLinkList(head);
else if (i == 3)
find(head);
else if (i == 4)
sort(head);
else if (i == 5)
display(head);
else if (i == 6)
merge(head);
else
printf("退出系统成功！！！\n");
}
}