C语言学习笔记10

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

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

void game()
{
	//生成随机数0-RAND_MAX之间
	int ret = rand()%100+1;  //生成1-100之间随机数
	int guess = 0;
	while (1)
	{
		printf("请猜数字:>");
		scanf("%d", &guess);
		if (guess > ret)
		{
			printf("猜大了\n");
		}
		else if (guess < ret)
		{
			printf("猜小了\n");
		}
		else
		{
			printf("恭喜你，猜对了\n\n");
			break;
		}
	}
}

int main()
{	
	//将三个数从大到小输出
	int a = 0;
	int b = 0;
	int c = 0;
	scanf("%d%d%d", &a, &b, &c);
	if (a < b)
	{
		int tmp = a;
		a = b;
		b = tmp;
	}
	if (a < c)
	{
		int tmp = a;
		a = c;
		c = tmp;
	}
	if (b < c)
	{
		int tmp = b;
		b = c;
		c = tmp;
	}
	printf("%d %d %d\n", a, b, c);

	//打印出1-100之间所有3的倍数
	int i = 0;
	for (i = 1; i <= 100; i++)
	{
		if (i % 3 == 0)
			printf("%d\n", i);
	}

	//数一下1到100的所有整数中出现多少个数字9
	int i = 0;
	int count = 0;
	for (i = 1; i <= 100; i++)
	{
		if (i % 10 == 9)
		{
			count++;
		}
		if (i / 10 == 9)
		{
			count++;
		}
	}
	printf("%d\n", count);

	//分数求和，计算1/1-1/2+1/3-1/4+1/5......+1/99-1/100的值
	int i = 0;
	double sum = 0.0;
	int flag = 1;
	for (i = 1; i <= 100; i++)
	{
		sum += flag * 1.0 / i;
		flag = -flag;
	}
	printf("%lf\n", sum);

	//求10个整数中的最大值
	int arr[10] = { 0 };
	int max = 0;
	int i = 0;
	int j = 0;
	for (j = 0; j <= 9; j++)
	{
		scanf("%d", &arr[j]);
	}
	int sz = sizeof(arr) / sizeof(arr[0]);
	for (i = 0; i < sz; i++)
	{
		if (arr[i] > max)
		{
			max = arr[i];
		}
	}
	printf("最大值 = %d\n", max);

	//在屏幕上输出9*9乘法口诀表
	int i = 0;
	for (i = 1; i <= 9; i++)
	{
		int j = 1;
		for (j = 1; j <= i; j++)
		{
			printf("%d*%d=%-2d  ", i, j, i*j);  //%2d这里打印两位，不够的用空格补在左边；%-2d空格补在右边
		}
		printf("\n");
	}
	printf("%4d", 100);  //不够的位数用空格补，超出则不做处理

	//猜数字游戏
	//1、电脑会生成一个随机数
	//2、猜数字对错
	int input = 0;
	srand((unsigned int)time(NULL));  
	//rand()前要调用srand() NULL空指针
	//时间戳：当前计算机的时间 - 计算机的起始时间(1970.1.1.0:0:0) = xxx秒
	//拿时间戳来设置随机数的生成起始点
	//time_t time(time_t* timer)
	do 
	{
		menu();
		printf("请选择>:");
		scanf("%d", &input);
		switch (input)
		{
		case 1:
			game();
			break;
		case 0:
			printf("退出游戏\n\n");
			break;
		default:
			printf("选择错误\n\n");
			break;
		}
	} while (input);



	return 0;
}