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Series column :【 from 0 To 1,C Language learning 】
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Preface

Sum up, analyze and realize the number guessing game , Shutdown Sequence , There are also some exercises for learning branches and cycles , Contains a simple and error prone written test question .

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Catalog

1️⃣ Realize the number guessing game
2️⃣ Shut down the applet
3️⃣ Branch and loop exercises

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.1 Guess the number game

Fulfill the requirements ： First print a menu on the screen , Generate a 1 To 100 Play a number guessing game with random numbers , Guess big or guess small , Until you're right ; To realize the game, you can play it all the time , Unless you don't want to play and choose to quit .

Setting a random number requires rand This function , Using this function requires a reference to the header file <stdlib.h>
rand The return value of the function is 0 To RAND_MAX Pseudo random integers in the range , Calling rand Before , Use srand Function to seed the pseudo-random number generator .

That is to say, they are using rand Function before , Need to use srand Set a random starting point ,rand To generate a real random number .
srand An unsigned integer argument is required , But if you just set a fixed integer , The random number generated by the first program execution is the same as that of running the program again after the first program execution , therefore srand The parameters here need to be variable , Here we will introduce the concept of timestamp ,

Use time function , Pay attention to the header file <time.h>, You can use the cast operator to change time() The return type of , The argument in this function is a pointer , If you don't want to use it, you can assign a null pointer to it srand((unsigned int)time(NULL));srand Function only needs to be set once to set the starting point in the program , Cannot be set more than once .

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

void menu()
{
    
	printf("######################\n");
	printf("########1.play########\n");
	printf("########0.exit########\n");
	printf("######################\n");

}


void game()
{
    
	// First get a random number 
	int a = 0;
	int ret = rand() % 100 + 1;
	while (1)// Cycle until you guess right, and the cycle ends 
	{
    
		printf(" Enter the number you guessed :>");
		scanf("%d", &a);// Enter the guessed number 
		if (a > ret)
		{
    
			printf(" Guess the \n");
		}
		else if (a < ret)
		{
    
			printf(" Guess a little \n");
		}
		else
		{
    
			printf(" It's too awesome , Guessed it \n");
			break;
		}
	}
}


int main()
{
    
	int input = 0;
	srand((unsigned int)time(NULL));// You can't put it in  game In a function or loop , Can only be set once 
	do
	{
    
		menu();// First print a menu to provide options 
		printf(" Please select :>");
		scanf("%d", &input);// Input selection 
		switch (input)
		{
    
		case 1:
			game();// The process of guessing numbers 

		case 0:
			break;
		default:
			printf(" Input error , Please re-enter \n");

		}

	} while (input);
	printf(" Game over \n");
	return 0;
}

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.2 Shut down the applet

strcmp Function to compare whether two strings are equal , Need a lead file <string.h>

system Function is used to execute system commands , Need a lead file <windows.h>
shutdown -s -t 60 Indicates setting the countdown 60 Shutdown in seconds
shutdown -a Indicates that the shutdown is cancelled

#include<stdio.h>
#include<windows.h>
#include<string.h>

int main()
{
    
	char input[30] = {
     0 };
	system("shutdown -s -t 120");
	while (1)
	{
    
		printf(" Please note that , Your computer will be in 120 Power off in seconds , Enter that I am a big baby to cancel the shutdown \n");
		scanf("%s", input);
		if (strcmp(input, " I'm a big baby ") == 0)
		{
    
			system("shutdown -a");
			break;
		}
	}
	return 0;
}

The part of canceling shutdown can be designed by ourselves , Can make this applet more interesting , For example, the part of canceling shutdown can be combined with the number guessing game above .
The code is as follows ：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include<windows.h>
#include<string.h>



void menu()
{
    
	printf("######################\n");
	printf("########1.play########\n");
	printf("########0.exit########\n");
	printf("######################\n");

}


int game()
{
    
	// First get a random number 
	int a = 0;
	int ret = rand() % 100 + 1;
	while (1)
	{
    
		printf(" Enter the number you guessed :>");
		scanf("%d", &a);
		if (a > ret)
		{
    
			printf(" Guess the \n");
		}
		else if (a < ret)
		{
    
			printf(" Guess a little \n");
		}
		else
		{
    
			printf(" It's too awesome , Guessed it \n");
			return 1;
		}
	}
}


int main()
{
    
	system("shutdown -s -t 120");
	printf(" Please note that , The game begins. Your computer will be in 120 Power off in seconds ,\n");
	printf(" Play a number guessing game , Guess right and cancel the shutdown \n");
	int input = 0;
	srand((unsigned int)time(NULL));
	do
	{
    
		menu();// First print a menu to provide options 
		printf(" Please select :>");
		scanf("%d", &input);
		switch (input)
		{
    
		case 1:
			if(game());// Realize the process of guessing numbers. If you guess right, return 1
			{
    
				system("shutdown -a");
			}
		case 0:
			break;
		default:
			printf(" Input error , Please re-enter \n");

		}

	} while (input);
	return 0;
}

You can put the code in Release Run in the environment to generate an executive program （exe file ）, Put this exe Documents can be sent to friends for entertainment , Of course, be careful not to play too much ！
Generate exe The procedure of the document is as follows ：

Then we can find one in the file directory where our project is located exe file , You can make a copy of this file and change its name .

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.3 Practice hand exercises

1. A written test question , See how many times it has to cycle

#include <stdio.h>
int main()
{
    
 int i = 0;
 int k = 0;
 for(i =0,k=0; k=0; i++,k++)
        k++;
 return 0;
}

It's easy to get wrong ： The judgment part is k = 0, instead of k == 0; So the judgment part is false , Not once .
2. Calculation n The factorial .

#include<stdio.h>
int main()
{
    
	int n = 0, i = 0,sum = 1;
	printf(" Who calculates the factorial :>");
	scanf("%d",&n);
	for (i = 1; i <= n; i++)
	{
    
		sum *= i;

	}

	printf("n The factorial of is :>%d\n",sum);

	return 0;
}

3. Calculation 1!+2!+3!+……+n!

#include<stdio.h>
// seek 1 To n Factorial and comparison of the two methods 

// The two methods are different in simplicity 


int main()// Method 1 is better 
{
    
	int ret = 1, sum = 0, i = 0,n = 0;
	scanf("%d",&n);
	for (i = 1; i <= n; i++)
	{
    
		ret *= i;
		sum += ret;

	}
	printf("%d\n",sum);
	return 0;
}


int main()// Method 2 
{
    
	int ret = 1, sum = 0, i = 0,j = 0,n = 0;
	scanf("%d",&n);

	for (i = 1; i <= n; i++)
	{
    
		ret = 1;
		for (j = 1; j <= i; j++)
		{
    
			ret *= j;
		}
		sum += ret;
	}

	printf("%d\n", sum);
	return 0;
}

4. Write code , Demonstrate the movement of multiple characters from both ends , Converging in the middle .

#include <stdio.h>
#include<windows.h>
int main()
{
    
	char arr1[] = {
     "My name is mrr" };
	char arr2[] = {
     "##############" };
	int left = 0, reight = strlen(arr1)-1;
	 Method 1 ： Use while Cycle to achieve 
	//while (left <= reight)
	//{
    
	// arr2[left] = arr1[left];
	// arr2[reight] = arr1[reight];
	// left++;
	// reight--;
	// printf("%s\n",arr2);
	// Sleep(1000);
	// system("cls");

	//}

	// Method 2 ： Use for Cycle to achieve  
	for (left = 0,reight = strlen(arr1)-1;left <= reight ;left++,reight--)
	{
    
		arr2[left] = arr1[left];
		arr2[reight] = arr1[reight];
		printf("%s\n", arr2);
		Sleep(1000);// Sleep 1 second 
		system("cls");// Clear the screen 
	}          // Pause after each character replacement 1 second , And then empty , Display the next replacement 
	printf("%s\n", arr2);
		return 0;
}

5. Write code to achieve , Simulate user login scenarios , And can only log in three times .
Only three passwords are allowed , If the password is correct, you will be prompted to log in as , If all three inputs are wrong , Then exit the program .

#include<stdio.h>
int main()
{
    
	char psw[10] = {
     "" };
	int i = 0;
	for (i = 1; i <= 3; i++)
	{
    
		printf(" Please input a password :>");
		scanf("%s",psw);
		if (strcmp(psw,"pasworld") == 0)
		{
    
			break;
		}
		
	}
	if (i == 4)
	{
    
		printf(" Three input errors , Log out ");
	}
	else
	{
    
		printf(" Login successful ");
	}

	return 0;
}

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Conclusion

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