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;
}