You need to make use of the begin and end method of the vector class, which return the iterator referring to the first and the last element respectively.
using namespace std;
vector
// push some strings in the vector.
myvector.push_back(“a”);
myvector.push_back(“b”);
myvector.push_back(“c”);
myvector.push_back(“d”);
vector
int n = 3; // nth element to be found.
int i = 0; // counter.
// now start at from the beginning
// and keep iterating over the element till you find
// nth element…or reach the end of vector.
for(it = myvector.begin(); it != myvector.end(); it++,i++ ) {
// found nth element..print and break.
if(i == n) {
cout<< *it << endl; // prints d.
break;
}
}
// other easier ways of doing the same.
// using operator[]
cout<
for (Iter it = vec.begin(); it!=vec.end(); ++it) {
sum += *it;
}
The advantage of using iterator is that you can apply the same pattern with other containers:
sum = 0;
for (Iter it = lst.begin(); it!=lst.end(); ++it) {
sum += *it;
}
For this reason, it is really easy to create template code that will work the same regardless of the container type.
Another advantage of iterators is that it doesn’t assume the data is resident in memory; for example, one could create a forward iterator that can read data from an input stream, or that simply generates data on the fly (e.g. a range or random number generator).
Another option using std::for_each and lambdas:
sum = 0;
std::for_each(vec.begin(), vec.end(), [&sum](int i) { sum += i; });
Since C++11 you can use auto to avoid specifying a very long, complicated type name of the iterator as seen before (or even more complex):
sum = 0;
for (auto it = vec.begin(); it!=vec.end(); ++it) {
sum += *it;
}
And, in addition, there is a simpler for-each variant:
sum = 0;
for (auto value : vec) {
sum += value;
}
And finally there is also std::accumulate where you have to be careful whether you are adding integer or floating point numbers.