字符串长度

sizeof()     strlen()  str.length.

1.strlen()

这个测字符数组长度，需要头文件 #include<cstring>

#include<iostream> 
#include<cstring> 
using namespace std; 
main () 
{ 
	char c[100005];
	cin >> c;
	int len = strlen(c);
	cout << len << endl;
}

2.sizeof()

测所占内存大小（就是在计算机中占几个字节）

#include<iostream> 
#include<cstring> 


using namespace std; 
main () 
{ 
	char c[100005];
	cin >> c;
	cout << "数组长度为" << endl;
	int len = strlen(c);
	cout << len << endl;
	cout << "c数组占字节长度为" << endl;
	int Csize = sizeof(c);
	cout << Csize << endl;
}

 

3.s.length()

用来测 string  定义的类的字符串长度

#include<iostream> 
#include<cstring> 
#include<string>

using namespace std; 
main () 
{ 

	string s;
	cin >> s;
	int len = s.length();
	cout << len << endl;
	
	int Ssize = sizeof(s);
	cout << Ssize << endl;
	

}