1、结构体
1.1 结构体基础知识
1.1.1 结构体类型的定义
struct Person{ char name[64]; int age; }; typedef struct _PERSON{ char name[64]; int age; }Person;
注意：定义结构体类型时不要直接给成员赋值，结构体只是一个类型，编译器还没有为其分配空间，只有根据其类型定义变量时，才分配空间，有空间后才能赋值。
1.1.2 结构体变量的定义
struct Person{ char name[64]; int age; }p1; //定义类型同时定义变量 struct{ char name[64]; int age; }p2; //定义类型同时定义变量 struct Person p3; //通过类型直接定义
1.1.3 结构体变量的初始化
struct Person{ char name[64]; int age; }p1 = {"john",10}; //定义类型同时初始化变量 struct{ char name[64]; int age; }p2 = {"Obama",30}; //定义类型同时初始化变量 struct Person p3 = {"Edward",33}; //通过类型直接定义
1.1.4 结构体成员的使用
struct Person{ char name[64]; int age; }; void test(){ //在栈上分配空间 struct Person p1; strcpy(p1.name, "John"); p1.age = 30; //如果是普通变量，通过点运算符操作结构体成员 printf("Name:%s Age:%d\n", p1.name, p1.age); //在堆上分配空间 struct Person* p2 = (struct Person*)malloc(sizeof(struct Person)); strcpy(p2->name, "Obama"); p2->age = 33; //如果是指针变量，通过->操作结构体成员 printf("Name:%s Age:%d\n", p2->name, p2->age); }
1.1.5 结构体赋值
1.1.5.1 赋值基本概念
相同的两个结构体变量可以相互赋值，把一个结构体变量的值拷贝给另一个结构体，这两个变量还是两个独立的变量。
struct Person{ char name[64]; int age; }; void test(){ //在栈上分配空间 struct Person p1 = { "John" , 30}; struct Person p2 = { "Obama", 33 }; printf("Name:%s Age:%d\n", p1.name, p1.age); printf("Name:%s Age:%d\n", p2.name, p2.age); //将p2的值赋值给p1 p1 = p2; printf("Name:%s Age:%d\n", p1.name, p1.age); printf("Name:%s Age:%d\n", p2.name, p2.age); }
1.1.5.1 深拷贝和浅拷贝
//一个老师有N个学生 typedef struct _TEACHER{ char* name; }Teacher; void test(){ Teacher t1; t1.name = malloc(64); strcpy(t1.name , "John"); Teacher t2; t2 = t1; //对手动开辟的内存，需要手动拷贝 t2.name = malloc(64); strcpy(t2.name, t1.name); if (t1.name != NULL){ free(t1.name); t1.name = NULL; } if (t2.name != NULL){ free(t2.name); t1.name = NULL; } } 1.1.6 结构体数组 struct Person{ char name[64]; int age; }; void test(){ //在栈上分配空间 struct Person p1[3] = { { "John", 30 }, { "Obama", 33 }, { "Edward", 25} }; struct Person p2[3] = { "John", 30, "Obama", 33, "Edward", 25 }; for (int i = 0; i < 3;i ++){ printf("Name:%s Age:%d\n",p1[i].name,p1[i].age); } printf("-----------------\n"); for (int i = 0; i < 3; i++){ printf("Name:%s Age:%d\n", p2[i].name, p2[i].age); } printf("-----------------\n"); //在堆上分配结构体数组 struct Person* p3 = (struct Person*)malloc(sizeof(struct Person) * 3); for (int i = 0; i < 3;i++){ sprintf(p3[i].name, "Name_%d", i + 1); p3[i].age = 20 + i; } for (int i = 0; i < 3; i++){ printf("Name:%s Age:%d\n", p3[i].name, p3[i].age); } }
1.2 结构体嵌套指针
1.2.1 结构体嵌套一级指针
struct Person{ char* name; int age; }; void allocate_memory(struct Person** person){ if (person == NULL){ return; } struct Person* temp = (struct Person*)malloc(sizeof(struct Person)); if (temp == NULL){ return; } //给name指针分配内存 temp->name = (char*)malloc(sizeof(char)* 64); strcpy(temp->name, "John"); temp->age = 100; *person = temp; } void print_person(struct Person* person){ printf("Name:%s Age:%d\n",person->name,person->age); } void free_memory(struct Person** person){ if (person == NULL){ return; } struct Person* temp = *person; if (temp->name != NULL){ free(temp->name); temp->name = NULL; } free(temp); } void test(){ struct Person* p = NULL; allocate_memory(&p); print_person(p); free_memory(&p); }
1.2.2 结构体嵌套二级指针
//一个老师有N个学生 typedef struct _TEACHER{ char name[64]; char** students; }Teacher; void create_teacher(Teacher** teacher,int n,int m){ if (teacher == NULL){ return; } //创建老师数组 Teacher* teachers = (Teacher*)malloc(sizeof(Teacher)* n); if (teachers == NULL){ return; } //给每一个老师分配学生 int num = 0; for (int i = 0; i < n; i ++){ sprintf(teachers[i].name, "老师_%d", i + 1); teachers[i].students = (char**)malloc(sizeof(char*) * m); for (int j = 0; j < m;j++){ teachers[i].students[j] = malloc(64); sprintf(teachers[i].students[j], "学生_%d", num + 1); num++; } } *teacher = teachers; } void print_teacher(Teacher* teacher,int n,int m){ for (int i = 0; i < n; i ++){ printf("%s:\n", teacher[i].name); for (int j = 0; j < m;j++){ printf(" %s",teacher[i].students[j]); } printf("\n"); } } void free_memory(Teacher** teacher,int n,int m){ if (teacher == NULL){ return; } Teacher* temp = *teacher; for (int i = 0; i < n; i ++){ for (int j = 0; j < m;j ++){ free(temp[i].students[j]); temp[i].students[j] = NULL; } free(temp[i].students); temp[i].students = NULL; } free(temp); } void test(){ Teacher* p = NULL; create_teacher(&p,2,3); print_teacher(p, 2, 3); free_memory(&p,2,3); }
