Windows下freopen函数使用与学生顺序表练习

该工程分为四个文件

main.cpp  主函数main所在文件，主要执行文件

student.h 各种函数(接口)的声明

student.cpp 各种函数(接口)的实现

studentInfo.txt  学生信息存储文件

1、freopen函数主要是重定向输入，

freopen("studentInfo.txt","r",stdin);//打开文件输入，以标准输入方式输入，重定向到studentInfo.txt
在C语言标准库中，并没有关闭freopen函数的方法，所以当要关闭时只能把它重定向到"CON"文件(DOS系统和Windows)

freopen("CON","r",stdin);  //关闭文件输入，重定向到控制台

当出现freopen函数无法关闭的情况可能是，你定义一个指针，没有分配空间，就执行写入操作，这会导致freopen出错（其实也是本身代码块出错），

2、主要代码

　　main.cpp

#include <iostream>
#include "stdint.h"
#include "student.h"
#include "string.h"

using namespace std;


int main() {
    SqList L;
    int n, id;
    float grade;
    char name[10];
    Position position;
    Student *student = new Student;

    cout << "Input student number:";
    cin >> n;

//  初始化
    init(L);

//  对顺序表进行数据初始化
    initData(L, n);  //以文件的方式传入学生信息
//  显示顺序表中数据信息
    printList(L);  //显示所有学生信息

// 删除测试
    cout << "Delete test:input a student's position which is you want to delete:";
    cin >> position;
    if (deleteStudent(L, position) == OK) cout << "Delete student who position =" << position << "
";

//  显示顺序表中数据信息
    printList(L);  //显示所有学生信息

//插入测试
    cout << "Input a id which is you want to insert student's id:";
    cin >> id;
    cout << "Input a grade which is you want to insert student's grade:";
    cin >> grade;
    cout << "Input a name which is you want to insert student's name:";
    cin >> name;
    cout << "Input a position which is you want to insert student position:";
    cin >> position;
    student->id = id;
    student->grade = grade;
    strcpy(student->name, name);
    if (insert(L, student, position) == OK) cout << "insert successful!
";
    else "This order table was full";
//  显示顺序表中数据信息
    printList(L);  //显示所有学生信息


//  查找测试
    cout << "Input a id which is you want to seek out student's name:";
    cin >> name;
    student = seek(L, name);
    if (student == NULL) cout << "Can't find student who is student's name=" << name << "
";
    else
        cout << "Found the student:
" << "student's id:" << student->id << "
" << "student's grade:" << student->grade
             << "
" << "student's name:" << student->name << "
";

//  返回顺序表长度
    cout << "The student's number is equal to:" << studentNum(L) << "
";


//  添加元素测试
    Student *student1 = new Student;
    cout << "Input a id which is you want to append student's id:";
    cin >> id;
    cout << "Input a grade which is you want to append student's grade:";
    cin >> grade;
    cout << "Input a name which is you want to append student's name:";
    cin >> name;
    student1->id = id;
    student1->grade = grade;
    strcpy(student1->name, name);
    if (append(L, student1) == OK) cout << "append student successful
";
    else "This order table was full
";
//  显示顺序表中数据信息
    printList(L);  //显示所有学生信息

//  返回顺序表长度
    cout << "The student's number is equal to:" << studentNum(L);
    delete student1;
    delete student;
}

　　student.h

#define MAXSIZE 10
enum Status{
    OK,
    ERROR
};
typedef int Position;
typedef struct {
    int id;
    char name[10];
    float grade;
} Student;

typedef struct {
    Student *student;
    int length;
} SqList;
/**
 * This function is called only at the beginning of the project;
 * @param L 传入顺序表的引用;
 * @return 返回是否成功创建一个空顺序表 return value: enum Status{OK,ERROR};
 */
Status init(SqList &L);

/**
 * This function is only used when the element is not full;
 * @param L 传入一个顺序表
 * @param student 传入一个student指针,该指针所指位置分配了空间存储操作的数据
 * @return 返回是否成功添加 return value: enum Status{OK,ERROR};
 */
Status append(SqList &L,Student* student);

/**
 * This function prints the data passed in to the sequence table;
 * @param L 传入一个顺序表
 */
void printList(SqList &L);

/**
 * This function is used to insert data into the order table;
 * @param L 传入一个顺序表
 * @param student 传入一个student指针,该指针所指位置分配了空间存储操作的数据
 * @param position 传入要操作的位置，注意该位置是从1开始，即student[0] belong to position one;
 * @return 返回是否成功插入 return value: enum Status{OK,ERROR};
 */
Status insert(SqList &L,Student* student,Position position);

/**
 *This function is used to delete the data with the specified position in the order tables;
 * @param L 传入一个顺序表
 * @param id 传入一个position 按照position delete student;
 * @return 返回是否成功删除 return value: enum Status{OK,ERROR};
 */
Status deleteStudent(SqList &L,Position position);

/**
 * This function is used to seek the data with specified id in the order tables;
 * @param L 传入一个顺序表
 * @param id 传入一个student's name 按照name查询数据
 * @return 返回一个student指针，该指针指向的内存分配了空间，存储返回的数据;
 */
Student* seek(SqList &L,char name[10]);
/**
 * This function is used to init order table;
 * @param L 传入一个顺序表
 * @param n 传入一个number,指代要录入的学生个数
 * @return 返回是否成功初始化数据 return value: enum Status{OK,ERROR};
 */
Status initData( SqList &L,int n);
/**
 * This function is used to return order table's length;
 * @param L 传入顺序表
 * @return 返回学生个数
 */
int studentNum(SqList &L);


student.cpp

#include "student.h"
#include "string.h"
#include <iostream>
using namespace std;

Status init(SqList &L) {
    L.student = new Student[MAXSIZE];
    if (!L.student) return ERROR;
    L.length = 0;
    return OK;
}

Status append(SqList &L, Student *student) {
    if (student == NULL) return ERROR;
    if (L.length == MAXSIZE) return ERROR;
    L.student[L.length].id = student->id;
    L.student[L.length].grade = student->grade;
    strcpy(L.student[L.length].name, student->name);
    L.length++;
    return OK;
}

void printList(SqList &L) {
    for (int i = 0; i < L.length; ++i) {
        cout << "id:" << L.student[i].id << " grade:" << L.student[i].grade << " name:" << L.student[i].name << "
";
    }
}

Status insert(SqList &L, Student *student, Position position) {
    int i = L.length;
    if (student == NULL) return ERROR;
    if (L.length == MAXSIZE) return ERROR;
    if (position > L.length || position < 0) return ERROR;
    while (position <= i) {
        L.student[i] = L.student[i - 1];
        i--;
    }
    L.student[position - 1].id = student->id;
    L.student[position - 1].grade = student->grade;
    strcpy(L.student[position - 1].name, student->name);
    L.length++;
    return OK;
}

Status deleteStudent(SqList &L, Position position) {
    if (position<=0||position>L.length) return ERROR;
    while (position<L.length){
        L.student[position-1] = L.student[position];
        position++;
    }
    L.length--;
    return OK;
}

Student* seek(SqList &L, char name[10]) {
    Student *student = new Student;
    for (int i = 0; i < L.length; ++i) {
        if (strcmp(L.student[i].name,name)==0) {
            student->id = L.student[i].id;
            student->grade = L.student[i].grade;
            strcpy(student->name, L.student[i].name);
            return student;
        }
    }
    return NULL;
}

Status initData(SqList &L,int n){
    Student *student = new Student;
    int id;
    float grade;
    char name[10];
    freopen("studentInfo.txt","r",stdin);//打开文件输入
    for (int i = 0; i < n; ++i) {
        cout << "Input student's id:";
        cin >> id;
        cout << "Input student's grade:";
        cin >> grade;
        cout << "Input student's name:";
        cin >> name;
        cout << "
";
        student->id = id;
        student->grade = grade;
        strcpy(student->name, name);
        if (append(L, student) == ERROR) {
            cout << i;
            break;
        }
    }
    freopen("CON","r",stdin);  //关闭文件输入
    return OK;
}

int studentNum(SqList &L){
    return L.length;
}


student.txt

1 56.5 tom
2 67.4 yom
3 98.5 uom
4 89.5 iom
5 90.5 oom
6 99.5 pom
7 34.7 gom
8 65.2 fom
9 112.5 nom
10 67.8 mom