如何将字符串的索引保存在向量中？

Question

Let's say I have a function int pozvec(vector<string> vect) which takes as parameter a pre-filled vector of strings.

I want to know at which position i there is the character "p", specifically "p" . All of the strings are single-character, but the vector is declared as containing strings. I want to save the index at which "p" is found in a variable x;

for(int i=0; i<vect.size(); i++)
    if(vect[i] == "p")
        x=i;

does not seem to work. Nor does strcmp , at all. The problem is more complex, but the part that doesn't work is this one.

Thank you in advance for your help!

Answer 1

By that function, your storing the index of the last occurrence of the string your looking for. This is because your not exiting from the loop once the first occurrence was found.

To exit from a loop conditionally, use the break statement.

for(int i = 0; i< vect.size(); i++)
{
    if(vect[i] == "p")
    {
        x=i;
        break;
    }
}

Now it will exit right after the first occurrence was found.

You also have another option in the form of std::find .

int index = std::find(vect.begin(), vect.end(), "P") - vect.begin()

Answer 2

I don't know what you really want to do, but this worked perfectly fine for me:

for (size_t i {}; i < vec.size(); ++i) {
   if (vec.at(i) == "p") {
       x = i;
       break; // I don't know wether you want to break here or not
   } else {
       continue;
   }
}

Or if you all strings include just one character this should also work:

for (size_t i {}; i < vec.size(); ++i) {
   if (vec.at(i).at(0) == 'p') {
       x = i;
       break; // I don't know wether you want to break here or not
   } else {
       continue;
   }
}