study c(vc中测试过)——结构体，链表，内存分配，位操作

#include "stdafx.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#define PEOPLE struct people
typedef struct people_l peoplelink;

//链表
struct people_l{
int age;
char *name;
struct people_l *next;
};

void main_struct(){
puts("start struct......");

struct people{
int age;
char *name;
}my3={30,"weisonghe3"};

struct people my,my2;
my.age=28;
my.name="weisonghe";
my2 = my;
my2.age=29;
printf("age=%d,name=%s/n",my.age,my.name);
printf("age=%d,name=%s/n",my2.age,my2.name);
printf("age=%d,name=%s/n",my3.age,my3.name);

//结构体指针
struct people *my4;
my4 = &my;
printf("age=%d,name=%s/n",(*my4).age,(*my4).name);
printf("age=%d,name=%s/n",my4->age,my4->name);
//指向结构数组的指针
struct people myarray[2]={{40,"www40"},{41,"www41"}};
struct people *structp=myarray;
structp=myarray;
for(int i=0;i<2;i++){
printf("name=%s/n",(*(structp+i)).name);
}
//结构指针变量作为函数参数

//动态分配函数
PEOPLE *dynamic=(PEOPLE*)malloc(sizeof(PEOPLE));
//(people*)即类型*为强制转换符,和函数返回类型格式一致
//*在类型前面表示变量，*在类型后面表示强制转换

dynamic->age=100;
dynamic->name="dynamicname";
printf("age=%d,name=%s/n",(*dynamic).age,(*dynamic).name);
free(dynamic);

//链表
peoplelink* create(int n);
peoplelink *pl = create(5);

for(peoplelink *temp = pl;temp!=NULL;temp = (*temp).next){
printf("age=%d,name=%s/n",(*temp).age,(*temp).name);
}

//枚举
enum week{monday,tuesday,wednesday,thursday,friday,saturday,sunday};
enum week w1,w2;
w1=saturday;
w2=(enum week)2;
printf("w1=%d,w2=%d/n",w1,w2);
}

char str[4][10];//声明全局变量，如果声明在for循环中，则结束后被释放
peoplelink* create(int n){

peoplelink *first ;
peoplelink *previous;
peoplelink *current;

for(int i=0;i<n;i++){
current = (peoplelink*)malloc(sizeof(peoplelink));
(*current).age=i;

//sprintf(str[i],"www%d",i);
//(*current).name=str[i];

char *temp = (char*)malloc(4);//使用手工动态分配内存，手工调用free才会释放
sprintf(temp,"www%d",i);
(*current).name=temp;

printf("--%d--%s/n",i,(*current).name);
if(i==0)
previous=first = current;
else
(*previous).next=current;//1、这里把previous指向的结构体变量的next变量地址指向current
(*current).next=NULL;
//2、指针传递的是地址，所以这里只是把previous指向的变量地址变为current的地址，而没有改变previous指向的变量的值
previous = current;
}

return first;
}

#include "stdafx.h"

void main_bit(){
puts("start bit main......");

//异或运算^，同为0，异为1
int a=9; //00010001
int b=a^5;//00000101
//00010100
printf("%d/n",b);

//求反运算～
int revert = ~a;
//9取反为11101110(负数的二进制在计算机中表示为补码：原码的反码+1)，因此原码为补码-1取反
//-1=11101101减一
// 10010010符号位不变取反即-10
printf("%d/n",revert);

//移位
int positive=-10;
printf("%d/n",positive>>1);//符号为不变，其他位右移一位，原数/2
printf("%d/n",positive<<1);//符号为不变，其他位左移一位，原数*2
//java中还包含>>>，用0填充前面的空位，而不是符号位

//位域
struct bitfield{
unsigned a:1;
unsigned b:3;
unsigned c:4;

};

struct bitfield bf1,*bf2;
bf1.a=1;
bf1.b=2;
bf1.c=4;
bf2=&bf1;
printf("%d,%d,%d/n",bf2->a,(*bf2).b,bf2->c);
}