分支和循环语句练习

一些简单的练习题

1.计算n的阶乘

#include <stdio.h>

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

下面用递归

#include <stdio.h>

int Factorial(int x)
{
	if (x <= 1)
		return 1;
	else
		return x * Factorial(x - 1);
}

int main()
{
	int n = 0;
	scanf("%d", &n);
	printf("%d\n", Factorial(n));
	return 0;
}

2.计算1！+2！+3！+…+ 10!

#include <stdio.h>

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

3.在数组中查找某个数

#include <stdio.h>

int main()
{
	int arr[] = { 1,2,3,4,5,6,7,8,9,10 };
	int sz = sizeof(arr) / sizeof(arr[0]);
	int left = 0;				//数组的起始位置
	int right = sz - 1;			//数组的末尾位置
	int mid;
	int k = 0;		//要查找的数字

	scanf("%d", &k);
	
	while (left <= right)
	{
		mid = left + (right - left) / 2;
		if (arr[mid] > k)
		{
			right = mid - 1;
		}
		else if (arr[mid] < k)
		{
			left = mid + 1;
		}		
		else
		{
			printf("找到了，下标为%d\n", mid);
			break;
		}			
	}

	if (left > right)
		printf("没找到\n");

	return 0;
}

二分查找

4.演示多个字符从两端移动，向中间汇聚

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

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

	while (left <= right)
	{
		arr2[left] = arr1[left];
		arr2[right] = arr1[right];
		printf("%s\n", arr2);

		left++;
		right--;
		Sleep(1000);	//在屏幕上显示1s，单位为ms
		system("cls");	//清空屏幕
	}

	printf("%s\n", arr2);
	return 0;
}

模拟用户登录情景，只能登录三次

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

int main()
{
	char passw[20]="password";	//原来的密码
	char pa[20];				//要输入的密码
	int i;
	for (i = 1; i <= 3; i++)
	{
		printf("请输入密码:");
		scanf("%s", pa);
		if (strcmp(pa, passw) == 0)		//strcmp函数：判断两个字符串是否相等
			break;
		else
			printf("密码错误,请重新输入\n");
	}
	if (i > 3)
	{
		printf("exit\n");
	}
	else
		printf("login in\n");
	return 0;
}

猜数字游戏

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

void menu()
{
	printf("************************\n");
	printf("****1.play    0.exit****\n");
	printf("************************\n");
	//printf("************************\n");
}

void game(int RandNum)
{
	int n;

	while (1)
	{
		printf("请猜数字(0~99):>");
		scanf("%d", &n);
		if (n > 0 && n < 99)
		{
			if (RandNum > n)
				printf("猜小了\n");
			else if (RandNum < n)
				printf("猜大了\n");
			else
			{
				printf("恭喜你!\n");
				break;
			}
		}
		else
			printf("请输入0到99的数字\n");
	}
	
}

int main()
{
	srand((unsigned)time(NULL));	//以时间戳为种子
	int RandNum = rand() % 99;		//随机生成0-99的数字
	int input = 0;
	do {
		menu();
		printf("请选择:>");
		scanf("%d", &input);
		switch (input)
		{
		case 1:
			game(RandNum);
			break;
		case 0:
			printf("退出游戏!\n");
			break;
		default:
			printf("输入错误!\n");
			break;
		}
	} while (input);
	//printf("%d\n", RandNum);
	return 0;
}