Question

Ok, I have another challenge. I have a question that asks me to “Read a set of integers into a vector. Print the sum of each pair of adjacent elements . Change your program so that it prints out the sum of the first and last elements, followed by the sum of the second and second-to-last, and so on.”

Currently I have managed to get it to add consecutive numbers, not exactly in pairs, but as close as I can get it.

The only operators I have learnt thus far for vectors, and what the question wants me to use are: v.empty(); v.size(); v.push_back(t); v[n]; v1 = v2; v1 = {a,b,c...}; v1 == v2; v1 != v2; <, <=, >, >=

Here is my code as it stands now:

#include <iostream>
#include <string>
#include <vector>

using std::string; using std::vector; using std::cout; using std::cin; using std::endl;

int main ()
{
    vector<unsigned> numbers {5, 6, 7, 8, 9, 10, 11};
    unsigned sum;

    decltype(numbers.size()) count;
    for (count = 0; count < numbers.size(); ++count){
        sum = (numbers[count]++) + (numbers[count]);
        cout << sum << " ";
    }
}

So I can get it to add 5+6; 6+7; 7+8 etc… but as for each pair and all the rest, not 100% sure where to start. Any guidance will be greatly appreciated!

Answer 1

Below two loops that print (1) sum of adjacent pairs and (2) the sum of opposite elements.

#include <cstddef>
#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main ()
{
    vector<unsigned> numbers {5, 6, 7, 8, 9, 10, 11};
    auto N = numbers.size();

    std::cout << "first part\n";
    for (size_t i = 1; i < N; ++i) {
       std::cout << numbers[i-1] + numbers[i] << "\n";
    }

    std::cout << "second part\n";
    for (size_t i = 0; i < (N - 1 - i); ++i) {       
      std::cout << numbers[i] + numbers[N - 1 - i] << "\n";   
    }
    // in case you have an odd number of elements
    if (N % 2 == 1) std::cout << numbers[N / 2] << "\n";

}

Output on LiveWorkSpace