Branch and loop statements

Branch statement

if - else

int main()
{
    
	if(condition)// expression 
	{
    
		// sentence 
	}
	int n = 3;
	if (n = 5)// =  Is assignment operator   Equivalent to if(5) It's not zero, it's zero true Executive judgment 
		printf("hehe\n");// prints hehe
	if (3 == n)// In order to prevent you from appearing, hit one less = You can put constants in front 
		// At this time, if you miss one = You're going to report a mistake 
		printf("hehe\n");
	int age = 10;
	if (18 < age <= 28)// This means to judge first age Is it greater than 18, no , return 0,0<=28
		//true  return 1  So it will print adult 
		// If we want to write such logic in mathematics, we should use  &&  Logical operators 
		printf(" adult \n");
	if (age > 18 && age <=28)
		printf(" adult \n");
	return 0;
}

int main()
{
    
	//if else  Without curly braces, you can only control the following line 
	// Add curly braces when controlling multiline statements 
	// also  else Only with the nearest if matching  
	// Add curly braces   It can make your logic clearer and avoid 
	// Indent unaligned logical confusion, etc 
	// So please develop excellent code style , Add curly braces 
	//int age = 10;
	//if (age < 18)
	// printf(" A minor \n");
	// printf(" Don't drink \n");
	//else
	// printf(" adult \n");
	//if (age < 18)
	// printf(" A minor \n");
	// if (age > 3)
	// printf("age=10");
	//else
	// printf("age !=10");
	int age = 10;
	if (age < 18)
	{
    
		printf(" A minor \n");
		printf(" Don't drink \n");
	}
	else
	{
    
		printf(" adult \n");
	}
	if (age < 18)
	{
    
		printf(" A minor \n");
	}
	
	if (age > 3)
	{
    
		printf("age=10");
	}
	else
	{
    
		printf("age !=10");
	}
	return 0;
}

switch

int main()
{
    
	//switch case  sentence 
	//switch(c) c Can not be float type  
	//case -  Only integer constant expressions   It can be characters, because characters store characters ASCII code 
	// Enter a case After the execution, use break end switch
	// Otherwise, he will perform other tasks in sequence case until switch end 
	// When the entered value does not case When the match , use default To receive all other values 
	// When multiple inputs are one result, please see the code writing below 
	int day = 0;
	scanf("%d", &day);
	switch (day)
	{
    
	/*case 1: printf(" Monday \n"); break; case 2: printf(" Tuesday \n"); break; case 3: printf(" Wednesday \n"); break; case 4: printf(" Thursday \n"); break; case 5: printf(" Friday \n"); break; case 6: printf(" Saturday \n"); break; case 7: printf(" Sunday \n"); break; default: printf(" Wrong choice \n"); break;*/
	case 1:
	case 2:
	case 3:
	case 4:
	case 5:
		printf("weekday\n");
		break;
	case 6:
	case 7:
		printf("weekend\n");
		break;
	default:
		printf(" Wrong choice \n");
		break;
	}
	return 0;
}

Please keep good programming habits , In the last case perhaps default Added in both break

Loop structure

while

int main()
{
    
	// Print 1-100 The odd number 
	// Both ideas are ok 
	int i = 1;
	while (i < 100)
	{
    
		//if (i % 2 == 1)
		//{
    
		// printf("%d ", i);
		//}
		//i++;
		printf("%d ", i);
		i += 2;
	}
	return 0;
}

int main()
{
    
	// Here are some knowledge points 
	// In fact, when we enter something on the keyboard ( such as asdadf\n) Enter to finish typing  --
	// It will be saved to an input buffer first (asdadf) --
	// This is when we use scanf getchar Taking data is taking data from the cache 
	//scanf You will encounter spaces , End getting data when entering  getchar Take only one data, no matter what 
	//EOF - end of file  End flag at the end of the file 
	// For example 
	// Suppose the password is a string 
	char password[20] = {
     0 };
	printf(" Please input a password >");
	scanf("%s", password);//asde enter  asaew asdq
	//getchar();// take \n Then the cache is empty , To let you choose Y/N
	// When there are many characters in your cache , So you need to empty the cache 
	int ch = 0;
	while ( (ch = getchar()) != '\n')//getchar The return type of is int 
	{
    
		;
	}
	printf(" Please confirm the password (Y/N):>");// Direct output NO  Don't let you choose 
	int ret = getchar();
	if (ret == 'Y')
	{
    
		printf("Yes\n");
	}
	else
	{
    
		printf("NO\n");
	}
//int ch = 0;
//while ( (ch = getchar()) != EOF)
//{
    
// putchar(ch);
//}
	return 0;
}

for

int main()
{
    
	// Let's see first while 
	int i = 0;// initialization 
	while ( i < 10)// Judge 
	{
    
		printf("%d ", i);
		i++;// adjustment 
	}
	return 0;
}

int main()
{
    
	//for Loop is the most commonly used loop 
	int i = 0;
	for (i = 0; i < 10; i++)//for Loop handle   initialization , Judge , Adjustments are put together 
	// So it's easier to understand 
	{
    
		printf("%d ", i);
	}
	// Our usual programming is   Way + Write code 
	// The solution is programming thinking   Writing code is to use computer language to realize thinking 
	// So the cultivation of thinking is very important 
	return 0;
}

int main()
{
    
	// About writing for Circular advice 
	//1. Not in for Modify the loop variable in the loop body , prevent for The cycle is out of control 
	//2. Suggest for The value of cyclic control variable is written in the form of front closed and back open interval ( Except for special circumstances )
	int i = 0;
	//for(i = 0; i <= 9 ;i++) [0,9]
	for (i = 0; i < 10; i++) // [0,10)  It's easier to understand what you're doing 
	{
    
		printf("%d ", i);
	// i = 12;
	}
	return 0;
}

int main()
{
    
	//for If the judgment part of the cycle is omitted, the condition is constant 
	for (;;)
	{
    
		printf("hehe\n");
	}
	return 0;
}

// seek 1*2*3...*n The factorial 
//1!+2!+3!...+n!
int main()
{
    
	int i = 0;
	int n = 0;
	int ret = 1;  
	//  When asked 20 Left and right factorial times , There will be overflow ,
	// This is beyond int Range of type values , Overflow is not discussed here 
	// For the implementation of large numbers, we need to rewrite a multiplication function for processing 
	int sum = 0; 
	scanf("%d", &n);
	for (i = 1; i <= n; i++)
	{
    
		ret *= i;
		sum += ret; //  Sum of factorials 
	}
	printf("%d\n", ret);
	printf("%d\n", sum);
	return 0;
}

do while

int main()
{
    
	//do while  That is, no matter what, directly cycle once and then judge 
	// To come up is to do !
	int i = 0; // initialization 
	do
	{
    
		printf("%d ", i);
		i++;// adjustment 
	} 
	while ( i < 10);// Judge 
	return 0;
}

int main()
{
    
	// Here we are talking about each cycle break and continue situation 
	int i = 0;
	//while (i < 10)
	//{
    
	// if (i == 5)
	// //break;// Print 0-4
	// continue;// Print 0-4 Post dead cycle 
	// printf("%d ", i);
	// i++;
	//}
	//for (i = 0; i < 10; i++)
	//{
    
	// if (i == 5)
	// //break;// Print 0-4
	// continue;// Print 0-4 6-9
	// printf("%d ", i);
	//}
	do
	{
    
		if (i == 5)
			//break;// Print 0-4
			continue;// Print 0-4 Post dead cycle 
		printf("%d ", i);
		i++;
	} while (i < 10);
	// In fact, this is because while,do while The adjustment of is continue Back ,
	//continue The function of is to jump out of this cycle , Do not execute the following statements and directly enter the next cycle 
	// therefore i Always equal to  5 
	return 0;
}

Add

int main()
{
    
	int i = 0;
	for (i = 0; i < 10; i++)
	{
    
		//for Each time the loop is executed, the loop body will be adjusted and then judged 
		// Initialization is performed once 
		printf("%d ", i);
	}
	return 0;
}