常用的函数
https://cplusplus.com/reference/ 没事儿多看看
1 数学函数
#include <math.h>
#include <stdio.h>
int main()
{
printf("%lf\n", sqrt(4));//开平方根——>double类型
printf("%lf\n", pow(2, 10));//求几次方的——>double类型
printf("%d\n", abs(-1));//整数绝对值
printf("%lf\n", fabs(-1.11));//浮点数的绝对值
//三角函数...
//对数函数...
return 0;
}
2 时间函数
可以做游戏用
#include <time.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <stdbool.h>
#include <windows.h>
void test_time_type()
{
clock_t t1; //其实就是long类型
time_t t2; //int64类型
size_t t3;
struct tm t4;//右击查看定义就能知道详细
/*struct tm
{
int tm_sec; // seconds after the minute - [0, 60] including leap second
int tm_min; // minutes after the hour - [0, 59]
int tm_hour; // hours since midnight - [0, 23]
int tm_mday; // day of the month - [1, 31]
int tm_mon; // months since January - [0, 11]
int tm_year; // years since 1900——>从1900年开始
int tm_wday; // days since Sunday - [0, 6]
int tm_yday; // days since January 1 - [0, 365]
int tm_isdst; // daylight savings time flag
};*/
}
//1 获取当前时间
void get_cur_time()
{
//1.使用time函数获取时间戳
time_t t = time(NULL);
//2.直接用ctime转换为字符串打印出来
puts(ctime(&t));
//3.时间戳转换为struct tm 自己去访问年月日时分秒
struct tm* pt = localtime(&t);
printf("%d年%d月%d日\n", pt->tm_year + 1900, pt->tm_mon + 1, pt->tm_mday);
printf("%02d:%02d:%02d\n", pt->tm_hour, pt->tm_min, pt->tm_sec);
//4.struct tm* 转换为字符串，内部有很多转换函数
puts(asctime(pt));
//5.格式化字符串
char buffer[50] = "";
strftime(buffer,50, "%Y-%m-%d %H:%M:%S", pt);
puts(buffer);
strftime(buffer, 50, "%F %T", pt);
puts(buffer);
}
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// 2 ！！！挺有用的，可以测自己写的算法运行时间间隔
void test_clock()
{
clock_t begin = clock();
for (int i = 0; i < 1000000; i++)
{
int a = i + 1;
int b = i + a;
int c = a + b + i;
}
clock_t end = clock();
printf("duration:%ld", end - begin);
}
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//3 ！！！定时器——>和sleep函数(会影响程序主循环)有区别的
bool on_timer(int duration, int id)
{
static int start_time[20] = { 0 };//静态变量，初始化代码只执行一次。普通变量每次都执行
if (start_time[id] == 0)
{
start_time[id] = clock();
}
int end_time = clock();
if (end_time - start_time[id] >= duration)
{
start_time[id] = end_time;
return true;
}
return false;
}
-----------------------------------------------------------------------------------------
//4 记录时间
void count_time(int duration)
{
time_t start_time, end_time;
int old_time = 0;
start_time = time(NULL);
while (1)
{
end_time = time(NULL);
int etime = (int)difftime(end_time, start_time);
if (old_time != etime)
{
printf("过去了 %d 秒\n", etime);
}
old_time = etime;
if(etime>=duration)
{
break;
}
}
}
-----------------------------------------------------------------------------------------
int main()
{
//get_cur_time();
//test_clock();
count_time(10);
//while (true)
//{
// printf("11111111\n");
// //Sleep(2000);
// if(on_timer(2000,0))
// printf("22222222\n");
//}
return 0;
}
3 随机函数
通常结合时间函数来做
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
//1 rand 和 srand
void test_rand()
{
//rand()——>伪随机数
//srand(100);//生成的随机树的最小值是100，随机函数种子，但也是伪随机数，可以与时间建立联系，就可以 真正随机了
//srand((unsigned int)time(NULL));
printf("%d\n", rand());
}
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//2 设置随机数范围
void set_rand()
{
//1.取余数 n%x [0,x-1]
printf("取余固定范围:%d\n", rand() % 10);
//2.n%x+a [a,x-1+a];
printf("最小值限定:%d\n", rand() % 10 + 5);
//3.某一个数字的整数倍
printf("整数倍:%d\n", rand() % 100 * 10);
}
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//与定时器结合(下面场景用)
bool on_timer(int duration, int id)
{
static int start_time[20] = { 0 };
if (start_time[id] == 0)
{
start_time[id] = clock();
}
int end_time = clock();
if (end_time - start_time[id] >= duration)
{
start_time[id] = end_time;
return true;
}
return false;
}
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//3 随机数两种应用场景
void test_use_rand()
{
//抽奖
int count = 1;
while (1)
{
int result = rand() % 1000;
printf("第%03d次抽奖结果:", count);
if (count>=100&&result == 0) //最少抽100次
{
printf("特等奖\n");
break;
}
else if (result >= 10 && result < 20)
{
printf("一等奖\n");
}
else if (result >= 100 && result <= 199)
{
printf("二等奖\n");
}
else if (result >= 300 && result <= 500)
{
printf("三等奖\n");
}
else
{
printf("安慰奖\n");
}
count++;
}
//游戏
int direct = 0;
while (1)
{
printf("怪物:");
//用上定时器
if (on_timer(1000, 0))
{
direct = rand() % 4;
}
switch (direct)
{
case 0:
printf("往上走!\n");
break;
case 1:
printf("往下走\n");
break;
case 2:
printf("往左走\n");
break;
case 3:
printf("往右走\n");
break;
}
}
}
int main()
{
test_rand();
set_rand();
test_use_rand();
return 0;
}
4 可增长函数
#include <stdarg.h>
#include <stdio.h>
/*
va_list
va_start
va_arg
va_end
...缺省符
*/
int sum(unsigned int count, int arg1, ...)
{
//创建参数列表，初始化
int result = arg1;
va_list start;
va_start(start, arg1);
for (int i = 1; i < count; i++)
{
result += va_arg(start, int);
}
va_end(start);
return result;
}
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//模拟自己写一个printf函数
//为什么要用'%d'之类的格式控制字符
void my_printf(const char* str, ...)
{
//做2种数据的解析
int inum = 0;
double dnum = 1.0;
va_list start;
va_start(start, str);
while (*str)
{
if (*str == '%')
{
str++;
switch (*str)
{
case 'd':
inum = va_arg(start, int);
printf("%d", inum);
break;
case 'f':
dnum = va_arg(start, double);
printf("%f", dnum);
break;
}
}
else
{
printf("%c", *str);
}
str++;
}
}
int main()
{
printf("sd\n");
printf("%d\n", sum(2, 1,2));
printf("%d\n", sum(3, 1,2,3));
printf("%d\n", sum(4, 1,2,3,4));
my_printf("整数 %d\t,小数%f", 12, 1.11f);
return 0;
}
5 其他头文件
有的函数很简单，可以自己封装
#include<ctype.h>//检查字符各种功能
#include <stdlib.h>//字符串转换，伪随机，动态内存，搜索，qsort....
#include <stdio.h>//输入输出，文件操作
#include <stdbool.h>//true和false
#include <iso646.h>//逻辑运算符用单词表示
#include <limits.h>//里面有最大最小正整数之类的宏
#include <string.h>//字符串操作
bool is_digit(char num)
{
//return num >= '0' && num <= '9';
return num >= '0' and num <= '9';
}
//qsort函数
int compare(const void* a, const void* b)
{
return (*(int*)a - *(int*)b);
}
int main()
{
isdigit('1');
printf("%d\n", INT_MAX);
printf("%d\n", INT_MIN);
----------------------------------------------------------------------------
//qsort函数
int values[] = { 40, 10, 100, 90, 20, 25 };
int n;
qsort(values, 6, sizeof(int), compare);
for (n = 0; n < 6; n++)
printf("%d ", values[n]);
----------------------------------------------------------------------------
//分割字符串
char str[] = "- This, a sample string.";
char* pch;
printf("Splitting string \"%s\" into tokens:\n", str);
pch = strtok(str, " ,.-");
while (pch != NULL)
{
printf("%s\n", pch);
pch = strtok(NULL, " ,.-");
}
return 0;
}
