没有用于调用strcmp的匹配函数

Question

I am new to c++ and currently am facing an error while using strcmp .

I have defined a structure as follows:

struct student
{
 string name;
 int roll;
 float marks;
 dob dobi;
 string dobp;
};
student *p;

And then, I am passing the pointer inside a function to sort it, like this:

void sortData(student *p)
{
 int a=0,b=0;
 for (a=0; a<=arraySize; a++)
 {
    for (b=a; b<=arraySize; b++)
    {
        if( strcmp(p[a].name, p[b].name) > 0 ) //Error
        {
           //sort logic yet to be implemented 
        }
    }
 }
}

Can someone please point out the mistake.

Error Message:

No matching function for call to strcmp

Answer 1

strcmp takes two const char* s for input - you need to convert your strings to C-style strings (assuming you're using std::string ) using std::string::c_str() :

if (strcmp(p[a].name.c_str(), p[b].name.c_str()) > 0)
//                  ^ Here             ^ and here

Answer 2

std::strcmp takes const char* as its parameter, while std::string doesn't match directly.

Because you're using std::string , you can just use operator>(std::basic_string)

if (p[a].name > p[b].name)

or use std::basic_string::compare

if (p[a].name.compare(p[b].name) > 0)