defining function using a struct - c++

Question

I'm a newbie to programming, especially to C++. I've got a task, and its part is to write a function using a struct.
struct S {
float m; //how many
int h; //where
float mx;
};
int main() {
S s;
s.m=0.5;
s.h=1;
vector<float> v(10);
for (int i=0;i<10;i++)
v[i]=sin(i);
S mx = max_search(v);
The function is ok, if (mx.m>0.98935 && mx.m<0.9894 && mx.h==8).
I came out with this code of function, but I know, it's quite defective.
float max_search(vector<float> v) {
int max=0;
for (int i=0; i<v.size(); i++) {
if (v[i]>max) {
max=v[i];
}
return max;
}
}
I don't know, what should I do with the type of function, and maybe the return value in also wrong.

Answer 1

Not sure I capture your main question correctly or not. You want to convert return value of max_search function which is float to struct S? I'll massage on KarithikT's answer and add more details:
To enable implicit conversion (from float to struct S), need to add conversion functions to S
struct S {
S():m(0.0), h(0), mx(0.0){ } //
S(float x):m(0.0), h(0), mx(x){ } // to enalbe convert float to S
float m; //how many
int h; //where
float mx;
};
float max_search(const vector<float>& v) { // pass by const reference
float max=0.0f;
for (int i=0; i<v.size(); i++) {
if (v[i]>max) {
max=v[i];
}
}
return max;
}
You could also use std::max_element to find max element from a container:
vector<float> v(10);
for (int i=0;i<10;i++) {
v[i]=sin(i);
}
S mx = *std::max_element(v.begin(), v.end());

Answer 2

You want your return max; In the outer most level. Right now it returns every iteration of the for loop, which means you get only 1 iteration.
float max_search(vector<float> v) {
float max=0.0f; <------------
for (int i=0; i<v.size(); i++) {
if (v[i]>max) {
max=v[i];
}
--------------
}
return max; <------------
}
And i think you want to call it like this s.mx = max_search(v);
You can also use std::max_element
s.mx = std::max_element(v.begin(),v.end()); // (begin(v),end(v)) in c++11

Answer 3

If you declare a function as float, why are you returning an int?
float max_search(vector<float> v) {
float max = v[0]; //this way you avoid an iteration
for (int i = 1; i < v.size() - 1; i++)
if (v[i] > max) max = v[i];
return max;
}
You can also use an iterator to do that:
float max_search(vector<float> v) {
float max = .0;
for (vector<float>::iterator it = v.begin(); it != v.end(); ++it)
if (*it > max) max = *it;
return max;
}
In the first code block it's important to substract 1 to v.size, other way you will try to access to an element that does not exists. If your code isn't returning you a segmentation fault, that's because std::vector is access safe. That means that std::vector try to access to the element, but anyway, you are doing one last innecesary iteration. That's why it's better to use iterators.
It's also true what #KarthikT says: you are trying to return max in each iteration, so, after first iteration, function return the value and stop the execution, always retrieving you the first value of the vector (if this value is greater than 0).
I hope this help.