C //习题 9.8 写一个函数insert，用来向一个动态链表插入结点。

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C程序设计（第四版）谭浩强习题9.8

习题 9.8 写一个函数insert，用来向一个动态链表插入结点。

IDE工具：VS2010

Note: 使用不同的IDE工具可能有部分差异。

代码块:

由于链表是动态链表，不能按照结构体变量为数组的时候通过指针增减调整指针指向，借鉴网上的提示，将原来的单链表增加一个结构体内指针，成为双向链表。

方法：使用指针，自定义类型，结构体，动态分配内存，函数返回类型调整为空。

#include <stdio.h>
#include <stdlib.h>typedef struct Student{int num;float score;Student *prev;Student *next;
}Student;void initialStu(Student **stu){int *n = (int*)malloc(sizeof(int));//输入要建立的学生人数printf("Enter the number of students: ");scanf("%d", n);while(*n <= 0){printf("Number can't less or equal than 0!\nEnter the number of students: ");scanf("%d", n);}printf("\n");//创建头结点，头结点的num指定为学生总人数Student *head = (Student*)malloc(sizeof(Student));head->num = *n;head->next = NULL;*stu = head;n = NULL;free(n);
}//判断学生编号是否重复
int isRepeat(Student *stu, int num){for(Student *p = stu->next; p != NULL; p = p->next){if(p->num == num){return 1;}}return 0;
}void creatStu(Student *stu){Student *head = stu;Student *p1 = head;Student *p2 = head;printf("Enter %d students info:\n\n", head->num);for(int i = 0; i < head->num; i++){p1 = (Student*)malloc(sizeof(Student));p1->next = NULL;p1->prev = p2;printf("Enter No.%d student number(100 ~ 999): ", i + 1);scanf("%d", &p1->num);while(p1->num < 100 || p1->num > 999 || isRepeat(stu, p1->num) == 1){if(isRepeat(stu, p1->num) == 1){printf("Number Repeat! ");}else{printf("Number Error! ");}printf("Retry!\nEnter No.%d student number(100 ~ 999): ", i + 1);scanf("%d", &p1->num);}printf("Enter No.%d student score(0 ~ 100): ", i + 1);scanf("%f", &p1->score);while(p1->score < 0 || p1->score > 100){printf("Score Error! Retry!\nEnter No.%d student score(0 ~ 100): ", i + 1);scanf("%f", &p1->score);}p2->next = p1;p1 = p1->next;p2 = p2->next;printf("\n");}
}void printStu(Student *stu){printf("\nThe info of %d students:\n", stu->num);for(Student *p = stu->next; p != NULL; p = p->next){printf("Number: %-4d  Score: %-6.2f\n", p->num, p->score);}printf("\n");
}void insertStu(Student *stu){Student *newStu = (Student*)malloc(sizeof(Student));printf("Enter new student info:\n\n");printf("Enter new student number(100 ~ 999): ");scanf("%d", &newStu->num);while(isRepeat(stu, newStu->num) == 1){printf("Number Repeat! Retry!\nEnter new student number(100 ~ 999): ");scanf("%d", &newStu->num);}while(newStu->num < 100 || newStu->num > 999 || isRepeat(stu, newStu->num) == 1){if(isRepeat(stu, newStu->num) == 1){printf("Number Repeat! ");}else{printf("Number Error! ");}printf("Retry!\nEnter new student number(100 ~ 999): ");scanf("%d", &newStu->num);}printf("Enter new student score(0 ~ 100): ");scanf("%f", &newStu->score);while(newStu->score < 0 || newStu->score > 100){printf("Score Error! Retry!\nEnter new student score(0 ~ 100): ");scanf("%f", &newStu->score);}printf("\n");//采用头结点后插入新结点Student *head = stu;newStu->next = head->next;head->next->prev = newStu;head->next = newStu;newStu->prev = head;
}int main(){Student *stu = NULL;initialStu(&stu);creatStu(stu);printStu(stu);insertStu(stu);printStu(stu);free(stu);system("pause");return 0;
}