c#练习题

#include<stdio.h>
int main() //代碼入口
{
	int a = 0;
	int n = 0;
	int p = 1;
	scanf("%d", &n);//scanf取n的地址，輸入n的值，開始for循環
	for (a = 1;a <= n;a++) {
		p = p * a;
	}
		printf("p=%d ", p);//輸出
}

#include<stdio.h>
int main()
{
  int i = 0, n, p = 1;
	for (n = 1;n <=10;n++)
	{
		p = p * n;
		i = i + p;
	}
	printf("1!+2!+3!+...+10!=%d", i);
	return 0;
}

#include<stdio.h>
int main()
{
	int arr[] = {1,2,3,4,5,6,8,9,10,11};
	int k =	7;

	int sz = sizeof(arr)/sizeof(arr[0]);//计算元素个数
	int left = 0;//左下标
	int right = sz-1;//右下标

	while(left<=right)
	{
		int mid = (left+right)/2;
		if(arr[mid] > k)
		{
			right = mid-1;
		}
		else if(arr[mid] < k)
		{
			left = mid+1;
		}
		else
		{
			printf("找到了,下标是：%d\n", mid);
			break;
		}
	}
	if(left>right)
	{
		printf("找不到\n");
	}
	return 0;
}

#include<stdio.h>
#include <string.h>
#include <windows.h>
#include <stdlib.h>
int main()
{
  
	char arr1[] = "welcome to bit!!!!!!";
	char arr2[] = "####################";
	int left = 0;
	//int right = sizeof(arr1)/sizeof(arr1[0])-2;//err
	int right = strlen(arr1)-1;

	while(left<=right)
	{
		arr2[left] = arr1[left];
		arr2[right] = arr1[right];
		printf("%s\n", arr2);
		//休息一秒
		Sleep(1000);
		system("cls");//执行系统命令的一个函数-cls - 清空屏幕
		left++;
		right--;
	}
	printf("%s\n", arr2);
	return 0;
}

int main()
{
	int i = 0;
	char password[20] = {0};
	for(i=0; i<3; i++)
	{
		printf("请输入密码:>");
		scanf("%s", password);
		if(strcmp(password, "123456") == 0)//== 不能用来比较两个字符串是否相等，应该使用一个库函数-strcmp
		{
			printf("登录成功\n");
			break;
		}
		else
		{
			printf("密码错误\n");
		}
	}
	if(i == 3)
		printf("三次密码均错误，退出程序\n");
	return 0;
}