C语言中，循环语句的应用练习

题目一：计算n的阶乘。

#include 

int main()
{
	int i = 0;
	int n = 0;
	int ret = 1;
	scanf("%d", &n);
	for (i = 1; i <= n; i++)
	{
		ret *= i;
	}
	printf("%dn", ret);

	return 0;
}

题目二：计算1!+2!+3!+......+10!

#include 

int main()
{
	int i = 1;
	int j = 1;
	int sum = 0;
	
	for (i = 1; i <= 10; i++)
	{
		int n = 1;
		for (j = 1; j <= i; j++)
		{
			n *= j;
		}

		sum += n;
	}
    printf("sum = %dn", sum);

	return 0;
}

#include 

int main()
{
	int n = 0;
	int ret = 1;
	int sum = 0;

	for (n = 1; n <= 10; n++)
	{
		ret *= n;
		sum += ret;
	}
	printf("%dn", sum);

	return 0;
}

题目三：在一个有序数组中查找具体的某个数字n。编写int binsearch(int x,intv[],int n);功能：在v[0]<=v[1]<=[2]<=......<=v[n-1]的数组中查找x

include 

int main()
{
	int arr[] = { 1,2,3,4,5,6,7,8,9,10 };
	int k = 7;//要查找的数字
	//在arr这个有序的数组中查找k（7）的值
	int sz = sizeof(arr) / sizeof(arr[0]);//数组的元素个数
	int left = 0;
	int right = sz-1;
	while (left<=right)
	{
		int mid = (left + right) / 2;
		if (arr[mid] < k)
		{
			left = mid + 1;
		}
		else if (arr[mid] > k)
		{
			right = mid - 1;
		}
		else
		{
			printf("找到了,下标是:%dn", mid);
			break;
		}
	}
	if (left > right)
	{
		printf("找不到了n");
	}
	return 0;
}

题目四：编写代码，演示多个字符从两端移动，向中间汇聚。

#include 
#include 
#include 

int main()
{
	char arr1[] = "Hello World!!!!!!";
	char arr2[] = "#################";
	int left = 0;
	int right = strlen(arr1)-1;

	while (left<=right)
	{
		arr2[left] = arr1[left];
		arr2[right] = arr1[right];
		printf("%sn", arr2);
		Sleep(1000);//睡眠1秒
		system("cls");//清空屏幕
		left++;
		right--;
	}
	printf("%sn", arr2);

	return 0;
}

题目五：编写代码实现，模拟用户登陆情景，并且只能登录三次。（只允许输入三次密码，如果密码正确则提示登陆成功，如果三次均输入错误，则退出程序）。

#include 
#include 

int main()
{
	int i = 0;
	//假设正确的密码是字符串"123456"

	char password[20] = { 0 };

	for (i = 0; i < 3; i++)
	{
		printf("请输入密码:>");
		scanf("%s", password);
		if(strcmp(password, "123456") == 0)
		{
			printf("登录成功n");
			break;
		}
		else
		{
			printf("密码错误，重新输入！n");
		}
	}
	if (i == 3)
		printf("三次密码均错误，退出程序n");

	return 0;
}