【C++】探索C++库函数的奇妙世界：深入了解如何发挥其强大功能

#include <iostream>
#include <cmath>

using namespace std;

int main() {
    // sqrt：计算平方根
    double squareRoot = sqrt(25.0);
    cout << "Square Root of 25: " << squareRoot << endl;

    // pow：计算指定数字的指定次方
    double powerResult = pow(2.0, 3.0);
    cout << "2^3: " << powerResult << endl;

    // fabs：计算浮点数的绝对值
    double absoluteValue = fabs(-10.5);
    cout << "Absolute Value of -10.5: " << absoluteValue << endl;

    // sin, cos, tan：计算正弦、余弦和正切值
    double angle = 45.0;
    cout << "Sin(45): " << sin(angle) << endl;
    cout << "Cos(45): " << cos(angle) << endl;
    cout << "Tan(45): " << tan(angle) << endl;

    // log, log10：计算自然对数和以10为底的对数
    double naturalLog = log(2.71828);
    cout << "Natural Log of 2.71828: " << naturalLog << endl;

    double logBase10 = log10(100.0);
    cout << "Log base 10 of 100: " << logBase10 << endl;

    // exp：计算指数函数
    double exponentResult = exp(1.0);
    cout << "e^1: " << exponentResult << endl;

    // floor, ceil：向下取整和向上取整
    double floorResult = floor(3.8);
    cout << "Floor of 3.8: " << floorResult << endl;

    double ceilResult = ceil(3.2);
    cout << "Ceil of 3.2: " << ceilResult << endl;

    // round：四舍五入到最近的整数
    double roundedValue = round(4.6);
    cout << "Rounded Value of 4.6: " << roundedValue << endl;

    // fmod：计算浮点数的余数
    double remainder = fmod(10.5, 3.0);
    cout << "Remainder of 10.5 / 3.0: " << remainder << endl;

    return 0;
}

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

int main() {
    // puts函数示例
    char str_puts[] = "Hello, World!";
    puts(str_puts);  //Hello, World!

    // gets函数示例
    char str_gets[100];
    printf("Enter a string: ");//输入：abc
    gets(str_gets);
    printf("You entered: %s\n", str_gets);//abc

    // strcat函数示例
    char dest_strcat[20] = "Hello, ";
    char src_strcat[] = "World!";
    strcat(dest_strcat, src_strcat);
    printf("strcat result: %s\n", dest_strcat);//Hello, World!

    // strcpy函数示例
    char dest_strcpy[20];
    char src_strcpy[] = "Hello, World!";
    strcpy(dest_strcpy, src_strcpy);
    printf("strcpy result: %s\n", dest_strcpy);//Hello, World!

    // strcmp函数示例
    char str1_strcmp[] = "apple";
    char str2_strcmp[] = "banana";
    int result_strcmp = strcmp(str1_strcmp, str2_strcmp);
    printf("strcmp result: %d\n", result_strcmp);//-1

    // strlwr函数示例
    char str_strlwr[] = "Hello, World!";
    strlwr(str_strlwr);
    printf("strlwr result: %s\n", str_strlwr);//strlwr result: hello, world!

    // strupr函数示例
    char str_strupr[] = "Hello, World!";
    strupr(str_strupr);
    printf("strupr result: %s\n", str_strupr);//strupr result: HELLO, WORLD!

    return 0;
}

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

char * merge(char * p1,char * p2){
    char * result=malloc(strlen(p1)+strlen(p2)+1);
    strcpy(result,p1);
    strcat(result,p2);
    return result;
}
int main(){
    const int MaxSize=100;
    char ch1[MaxSize],ch2[MaxSize];

    fgets(ch1,MaxSize,stdin);
    fgets(ch2,MaxSize,stdin);

    // 去除换行符
    ch1[strcspn(ch1, "\n")] = '\0';
    ch2[strcspn(ch2, "\n")] = '\0';

    char *p1=ch1,*p2=ch2;

    char *result=merge(p1,p2);
    printf("%s",result);

}