c++学习-字符串

 

字符数组和 string类型比较的区别

#include<iostream>
#include<string>
using namespace std;

class area{
public:
    area(){ cout << "gouzao:" <<endl; }
    area(int i){ this->i = i; cout << "gouzao:" << i << endl; }
    area(int w, int h){ this->w = w; this->h = h; cout << "gouzao" << endl; }
    ~area(){ cout << "xigou "<<i << endl; }
    int get()
    {
        return w*h;
    }
    void set(int w, int h)
    {
        this->w = w;
        this->h = h;
    }
private:
    int w;
    int h;
    int i;
};


int main()
{

    //char 数组做比较需要 strcmp
    //char a[] = "ab";
    //char b[] = "ab";
    //cout << (a==b) << endl;//不相等，比较的是两个地址

    //cout << strcmp(a, b) << endl;
    //cout << strcmp(a, "ab") << endl;

    string a = "ab";

    cout << (a == "ab") << endl; //wright


    return 0;

}

 

赋值比较：

int main()
{

    char ch1[10] = "ab";
    char ch2[10] = "cd";

    //ch1 = ch2;  //错误
    strcpy(ch1, ch2);

    string ch3 = "ab"; 
    string ch4 = "cd";
    
    ch3 = ch4;

    cout << ch3 << endl;
    cout << ch4 << endl;

    return 0;

}

 

字符串赋值：

#include<iostream>
#include<string>
using namespace std;

class area{
public:
    area(){ cout << "gouzao:" <<endl; }
    area(int i){ this->i = i; cout << "gouzao:" << i << endl; }
    area(int w, int h){ this->w = w; this->h = h; cout << "gouzao" << endl; }
    ~area(){ cout << "xigou "<<i << endl; }
    int get()
    {
        return w*h;
    }
    void set(int w, int h)
    {
        this->w = w;
        this->h = h;
    }
private:
    int w;
    int h;
    int i;
};


int main()
{

    //char ch1[10] = "ab";
    //char ch2[10] = "cd";

    ////ch1 = ch2;  //错误
    //strcpy(ch1, ch2);

    string ch3 = "ab"; 
    string ch4 = "cd";
    
    ch3 = ch4;

    ch3.assign(ch4,0,1); //部分元素赋值给ch3

    cout << ch3 << endl;
    cout << ch4 << endl;

    return 0;

}

 

字符串合并：

int main()
{

    string ch1 = "ab";
    string ch2 = "cd";

    ch1 = ch1 + ch2;

    cout << ch1 << endl;
    cout << ch2 << endl;

    return 0;

}

 

计算长度：

int main()
{

    string ch1 = "ab";
    string ch2 = "cd";

    ch1 = ch1 + ch2;

    cout << ch1 << endl;
    cout << ch2 << endl;

    //计算字符长度
    cout << strlen(ch1.c_str()) << endl;
    cout << ch1.size() << endl;
    cout << ch1.length() << endl;


    return 0;

}

 

字符串部分合并：

int main()
{



    //char ch3[10] = "ab";
    //char ch4[10] = "abcdefg";

    //strncat(ch3, ch4, 3);

    //cout << ch3 << endl;

    string ch1 = "ab";
    string ch2 = "cdefg";

    ch1.append(ch2, 2,2);
    cout << ch1 << endl;

    return 0;

}

 

字符串替换：

int main()
{

    //char ch3[10] = "ab";
    //char ch4[10] = "abcdefg";

    //strncpy(ch3, ch4, 3);

    //cout << ch3 << endl;

    string ch1 = "ab";
    string ch2 = "cdefg";
    char ch5[] = "cdefg";
    char ch6 = 'A';

    //ch1.replace(0,1,ch2, 2,2);
    //ch1.replace(0, 1, ch5, 2, 2);//支持char型数组
    //ch1.replace(0, 1, 2, ch6);//支持char 字符



    cout << ch1 << endl;

    return 0;

}

 

字符串拷贝：

int main()
{

    char ch3[10] = "abffffff";
    char ch4[10] = "abcdefg";

    memmove(ch3, ch4, 4);

    cout << ch3 << endl;

    string ch1 = "abcdefghkjklmn";
    char ch5[] = "cdefg";

    cout << ch5 << endl;
    
    ch1.copy(ch5,2,3);

    cout << ch5 << endl;

    return 0;

}

 

字符串插入：

int main()
{

    string str1 = "abcdefg";
    string str2 = "abc"; 

    str1.insert(2,str2, 0,2);

    cout << str1 << endl;

    return 0;

}

 

字符串删除：

int main()
{

    string str1 = "abcdefg";
    str1.erase(2,2);

    cout << str1 << endl;

    return 0;

}

 

删除字符串：

int main()
{

    string str1 = "abcdefg";
    str1.erase(2,2);
    cout << str1 << endl;

    str1.erase(2);//第二个以后全部删除
    cout << str1 << endl;

    str1.erase();//清空一个字符串
    cout << str1 << endl;


    return 0;

}

 

字符串查找：

int main()
{
    char ch1[15] = "hello world!";
    char *p, c = '4';

    p = strchr(ch1, c);//返回找到的w字符的地址，找不到则返回空指针

    if (p)
    {
        cout << p << endl;
        cout << p - ch1 << endl; //计算找到的字符的下标
    }
    
    return 0;

}

int main()
{
    string str1("abcdefg");

    int f = str1.find('b', 1); //从第一个字符开始查找

    if (f == string::npos)
    {
        cout << "not find " << endl;
    }
    cout << f << endl;

    f = str1.find_first_not_of('b', 1); //查找第一个不是b的字符
    cout << f << endl;

    f = str1.find_last_of('b'); //查找最后一个b的位置

    cout << (int)string::npos << endl;
    
    return 0;

}

 

判断字符串是否为空：

int main()
{
    
    string s1 = "";
    
    if (s1.empty())
    {
        cout << "empty" << endl;
    }else{
        cout << "not empty" << endl;
    }
    return 0;

}

 

字符串交换：

int main()
{
    char ch1[15] = "ofru";
    char ch2[15] = "";
    swap(ch1,ch2);

    cout << ch1 << endl;
    cout << ch2 << endl;

    string str1 = "ab";
    string str2 = "";
    str1.swap(str2);

    cout << str1 << endl;
    cout << str2 << endl;

    return 0;

}

 

string字符串转char型

int main()
{
    string str1 = "abcde";

    const char *p;
    p = str1.c_str();

    cout << p << endl;

    return 0;

}

 

字符串传参：

int get_length(const char *p)
//int get_length(const char p[])
{
    int count = 0;
    while (*p)
    {
        count++; 
        p++;
    }

    return count;
}

int main()
{

    char a[] = "abc";
    char *p = "defg";

    cout << get_length(a) << endl;
    cout << get_length(p) << endl;

    return 0;

}

 

字符串函数返回：

char *get(const char *str)
{
    char *p = new char[strlen(p) +1];
    strcpy(p, str);

    return p;
}

int main()
{

    char a[] = "abc";
    char *p = get(a);

    cout << p << endl;

    char *p2 = get("abc");
    cout << p << endl;

    char *p3 = "abc";
    char *p4 = get(p3);
    cout << p4 << endl;

    delete[]p;

    return 0;

}

 

结构体：

#include<iostream>
#include<string>
using namespace std;

struct man{
public:
    int age;
    char *name;

};

int main()
{
    struct man one={
        12,
        "中国"
    };

    cout << one.age << endl;
    cout <<one.name<< endl;

    return 0;

}

 

结构体与构造函数：

#include<iostream>
#include<string>
using namespace std;

struct man{
    man(int c_age);
//public:
    int age;
    char *name;
    string name1;

};

man::man(int c_age)
{
    age = c_age;
}

int main()
{
    man one(4);

    cout << one.age << endl;
    
    return 0;
}

 

结构体赋值：

#include<iostream>
#include<string>
using namespace std;

struct man{
    int age;
    char *name;
    string name1;

};


int main()
{
    man one = {
        1, "one", "one1"
    };

    man two = {
        1, "two", "two1"
    };

    one = two;

    cout << one.age << endl;
    cout << one.name << endl;
    cout << one.name1 << endl;
    
    return 0;
}

 

结构体与函数：

#include<iostream>
#include<string>
using namespace std;

struct time{
    int hour;
    int minute;
};

const int perhour = 60;
time sum(time t1, time t2);

int main()
{

    time t1 = {23,4};
    time t2 = { 5, 14 };

    time total = sum(t1,t2);

    cout << total.hour << endl;
    cout << total.minute << endl;
    
    return 0;
}

time sum(time t1, time t2)
{
    time total;
    total.minute = (t1.minute + t2.minute) % perhour;
    total.hour = t1.hour + t2.hour + ((t1.minute + t2.minute) / perhour); 

    return total;

}

 

指针方式返回：

#include<iostream>
#include<string>
using namespace std;

struct time{
    int hour;
    int minute;
};

const int perhour = 60;
time *sum(const time &t1, const time &t2);

int main()
{
    time t1 = {23,4};
    time t2 = { 5, 14 };

    time *total = sum(t1,t2);

    cout << total->hour << endl;
    cout << total->minute << endl;
    
    return 0;
}

time *sum(const time &t1, const time &t2)
{
    time *total = new time;
    total->minute = (t1.minute + t2.minute) % perhour;
    total->hour = t1.hour + t2.hour + ((t1.minute + t2.minute) / perhour); 

　　delete total;
    return total;

}

 

引用方式传递返回：

#include<iostream>
#include<string>
using namespace std;


const string &show(const string &str);

int main()
{
    
    string str1 = "abc";
    string str2 = show(str1);
 
    cout << str2 << endl;


    return 0;
}

const string &show(const string &str)
{
    return str;
}