## 选择结构

### 选择结构-1

![image-20250220225958223](https://yp.smallkun.cn/markdown/image-20250220225958223.png!compress)

```c
#include <stdio.h>

/*
if(条件){
	复合语句(条件为真时执行) 
}else{
	复合语句(条件为假时执行) 
}
*/
int main(void){

	int x, y, z, t;//定义三个整型变量
	//数据类型 变量名1, 变量名2;
	scanf("%d%d%d", &x, &y, &z);
	if(x > y){
		t = x;
		x = y;
		y = t;
	}//实现x和y比较 大数放y位置 
	if(y > z){
		t = y;
		y = z;
		z = t;
	}//实现y和z比较 大数放z位置 z为三个数字中最大数
	if(x > y){
		t = x;
		x = y;
		y = t;
	}
	printf("%d %d %d\n", x, y, z);
	
	return 0;
}

```

### 选择结构-2

![image-20250220230052521](https://yp.smallkun.cn/markdown/image-20250220230052521.png!compress)

```c
#include <stdio.h> 

int main(void){
	
	
	int a;
	
	scanf("%d", &a);
	printf("该数的位数为%d\n", 
	(a/10==0?1:(a/100==0?2:(a/1000==0?3:(a/10000==0?4:5)))));
	printf("%d", a%10);
	if(a%100/10 != 0){
		printf("%d", a%100/10);
	}
	if(a%1000/100 != 0){
		printf("%d", a%1000/100);
	}
	if(a%10000/1000 != 0){
		printf("%d", a%10000/1000);
	}
	if(a/10000 != 0){
		printf("%d", a/10000);
	}
	printf("\n");
	return 0;
}

```

### 选择结构-3

![image-20250220230133563](https://yp.smallkun.cn/markdown/image-20250220230133563.png!compress)

```c
#include <stdio.h>

int main(void){
	
	float a, b, result;
	int flag;
	printf("请输入两个数字:");
	scanf("%f %f", &a, &b);
	printf("请输入您要进行的操作(1.做加法 2.做乘法 3.做除法):");
	scanf("%d", &flag);
	switch(flag){
		case 1:result = a+b;break;
		case 2:result = a*b;break;
		case 3:result = a/b;break;
	}
	printf("结果为%f\n", result);
	
	return 0;
}

```

### 选择结构-4

![image-20250220230626411](https://yp.smallkun.cn/markdown/image-20250220230626411.png!compress)

```c
#include <stdio.h>

int main(void){
	
	int year, month, day, days=0;
	
	scanf("%d-%d-%d", &year, &month, &day);
	days+=day;
	//1 3 5 7 8 10 12
	//从前一个月开始依次 
	switch(month-1){
		case 11:days+=30;
		case 10:days+=31;
		case 9:days+=30;
		case 8:days+=31;
		case 7:days+=31;
		case 6:days+=30;
		case 5:days+=31;
		case 4:days+=30;
		case 3:days+=31;
		case 2:days+=28;
		case 1:days+=31;
	}
	if(month>3 && (year%4==0&&year%100!=0 || year%400==0)){
		days++;
	} 
	printf("%d\n", days);
	
	
	return 0;
}
```

---

## 循环结构

### 循环结构-1

![image-20250220230645828](https://yp.smallkun.cn/markdown/image-20250220230645828.png!compress)

```c
#include <stdio.h>


/*
1.解决字符的循环输入
while((ch=getchar())!='\n')

2.判断字符类型
ASCALL码范围 

*/
int main(){
	
	char ch;
	int l, d, o;//l字母的个数 d为数字个数 o为其他字符个数
	l=d=o=0;
	while((ch=getchar()) != '\n'){
		if(ch >= 'a' && ch<='z' || ch >= 'A' && ch<='Z' ){
			l++;
		}else if(ch >= '0' && ch <= '9'){
			d++;
		}else{
			o++;
		}
	} 
	printf("字母个数:%d 数字个数:%d 其他个数%d\n", l, d, o);	
	
	return 0;
}
```

### 循环结构-2

![image-20250220230945704](https://yp.smallkun.cn/markdown/image-20250220230945704.png!compress)

```c
/*
暴力求解+枚举每一个台阶
for(i=0;i<1000;i++){
		
}
i=0;
while(i<1000){
	
	i++;
}
&& || !
表达式1&&表达式2
左右都为真才为真
短路运算 表达式1为假 表达式2直接不运算 直接为假 
*/

#include <stdio.h>

int main(){
	int i;
	for(i=0;i<1000;i++){
		if(i%2==1 && i%3==2 && i%5==4 && i%6==5 && i%7==0){
			printf("台阶数为%d\n", i);
			break;
		}
	}
	
	
	
	
	return 0;
}
```

### 循环结构-3

![image-20250220230952843](https://yp.smallkun.cn/markdown/image-20250220230952843.png!compress)

```c
#include <stdio.h>
/*
大马:i
中马:j
小马:k 
*/

int main(){
	int i, j , k;
	for(i=0;i<=33;i++){
		for(j=0;j<=50;j++){
			for(k=0;k<=200;k+=2){
				if(i+j+k==100 && i*3 + j*2 + k/2 == 100){
					printf("大马:%-2d 中马:%-2d 小马:%-2d\n", i, j, k);
				}
			}
		}
	}
	
	
	return 0;
}
```

### 循环结构-4

![image-20250220231000056](https://yp.smallkun.cn/markdown/image-20250220231000056.png!compress)

```c
#include <stdio.h>

int main(){
	
	int i, s, t;//i用来遍历所有数, s用来存储数的位数,t是截取掉最高位之后的数 
	for(i=1;i<9999;i++){
		t = i;
		while(t > 0){
			s = (t/10==0?1:(t/100==0?2:(t/1000==0?3:4)));//求出这个数字位数
			t = i%(int)pow(10, s-1);//使用模除去掉最高位 
			if(t*t == i){
				printf("%d:%d\n", t, i);
			}
		}
	}
	
	
	
	return 0;
}
```

### 循环结构-5

![image-20250220231006104](https://yp.smallkun.cn/markdown/image-20250220231006104.png!compress)

```c
#include <stdio.h>

int main(){
/*
	int x, n, t=1;//t为2当前需要加入的位置 
	
	scanf("%d", &x);
	n = x;//处理之后数
	while(t < x){//判断位置是否超过的数的范围 
		n+=t*2;
		//根据当前输入位置判断前一位是否溢出如果溢出则减一 
		if(n/(t*10) != x/(t*10)){
			n-=(t*10);
		}
		t*=10;//继续处理下一位 
	}
	printf("%d:%d\n", x, n);
*/
	int x, s = 0;
	scanf("%d", &x);
	while(x){
		s*=10;
		s += (x%10+2)%10;
		x /= 10;
	}
	for(;s;s/=10){
		printf("%d", s%10);
	}

	return 0;
}
```

### 循环结构-6

![image-20250220231012110](https://yp.smallkun.cn/markdown/image-20250220231012110.png!compress)

```c
```

### 循环结构-7

![image-20250220231022607](https://yp.smallkun.cn/markdown/image-20250220231022607.png!compress)

```c
```

### 循环结构-8

![image-20250220231027969](https://yp.smallkun.cn/markdown/image-20250220231027969.png!compress)

```c
```

### 循环结构-9

![image-20250220231034218](https://yp.smallkun.cn/markdown/image-20250220231034218.png!compress)

```c
```

### 循环结构-10

![image-20250220231039716](https://yp.smallkun.cn/markdown/image-20250220231039716.png!compress)

```c
```

---

## 数组

### 数组-1

![image-20250220231426147](https://yp.smallkun.cn/markdown/image-20250220231426147.png!compress)



### 数组-2

![image-20250220231434409](https://yp.smallkun.cn/markdown/image-20250220231434409.png!compress)



### 数组-3

![image-20250220231441384](https://yp.smallkun.cn/markdown/image-20250220231441384.png!compress)



### 数组-4

![image-20250220231447834](https://yp.smallkun.cn/markdown/image-20250220231447834.png!compress)



### 数组-5

![image-20250220231704799](https://yp.smallkun.cn/markdown/image-20250220231704799.png!compress)

---

## 函数



## 指针



## 编译预处理



## 结构体



## 文件

##