嵌入式学习笔记19.11.27
c语言共用体:
#include <stdio.h>
union st{
int x;
char a;
char s[10];
}student;
int main(){
scanf("%d",&student.x);
getchar();
printf("%d\n",student.x);
printf("%d\n",student);
scanf("%c",&student.a);
getchar();
printf("%c\n",student.a);
printf("%c\n",student);
}
//共用体大小，占用共用体最大元素大小
//存数据的瞬间是最后一次赋的值
//运行谁存谁，值为最后存储的数据
//共用体一般用于临时数据
c语言枚举:
#include <stdio.h>
//枚举
enum color{
red,blue,yellow = 10,black,white = 20,pink
};
enum select{
A,B,C,D
}sel;
int main(){
printf("%d\n",red);
printf("%d\n",blue);
printf("%d\n",yellow);
printf("%d\n",black);
printf("%d\n",white);
printf("%d\n",pink);
switch(sel){
case A:printf("666");break;
case 1:printf("888");break;
}
}
//枚举默认第一项为0，第二项为1，以此类推
// 若第n项为10，则n+1项为11，以此类推
//对于选项进行整型判断
c语言二分法:
#include <stdio.h>
#define N ((a+b)/2)
#define M ((a+b+1)/2)
int main(){
int a = 0,b = 9,c = N,n,flag = 0;
while(1){
printf("请输入：");
scanf("%d",&n);
int s[10] = {1,4,7,12,15,27,36,49,51,63};
while(flag == 0){
if(s[c] > n){
b = c;
c = N;
}
else if(s[c] < n){
a = c + 1;
c = M;
}
else if(s[c] == n){
flag = 1;
break;
}
if(a == b){
flag = 2;
break;
}
}
if(flag == 1){
printf("数组的第%d个数\n",c+1);
}
if(flag == 2){
printf("查找的值不存在\n");
}
a = 0;b = 9;c = N;flag = 0;
}
}
//两种数据处理的方式：
//队列，先到先处理
//栈，先到后处理
//数据查找方式：（有序：小到大或大到小 数组）二分法：
//a[10] = {1, 4, 7, 12, 15, 27, 36, 49, 51, 63}
// ^
// |
//不能整除2就都+1/-1
//(0+9-1)/2 ?15
//(5+9-1)/2 ?36
//(6+9-1)/2 ?49√
//若上限与下限值相等都没有,就是没有数据
c语言单链表
#include <stdio.h>
#include <stdlib.h>
struct stu{
int m;
char a;
struct stu *next;//!!结构体指针是4个字节
};
struct stu student[5];
int main(){
int i;
struct stu *head;
if(head == NULL){
head = (struct stu*)malloc(sizeof(stu));
}
//head -> m = 1;
scanf("%d",&head->m);
//head -> a - 'g';
scanf("%d",&head->a);
struct stu *next;
for(i = 0;i < 5;i++){
next = (struct stu*)malloc(sizeof(stu));
scanf("%d",&next->m);
scanf("%c",&next->a);
}
//head -> next = (struct stu*)malloc(sizeof(stu));
//head -> next -> m = 2;
//head -> next -> a = 'h';
//head -> next -> next = (struct stu*)malloc(sizeof(stu));
//head -> next -> next -> m = 3;
//head -> next -> next -> a = 'i';
}
//链表,在结构体的基础上
//定义当前结构体类型的指针
//malloc在内存内申请空间<stdlib.h>
//free(指针)释放空间
//typedef int u32
//之后的代码u32等同于int
