Vectors and strings

Consider the following program that "finds" even integer values stored in an std::vector<int> vect and grows another std::vector<int> even_values with copies of the even integers values found.

#include <iostream>
#include <vector>
 
int main() {
  std::vector<int> vect{1, 2, 3, 4, 5}; // creates an std::vector<int&gt storing 1, 2, 3, 4, 5
  std::vector<int> even_values; // init an empty std::vector<int>
  for (unsigned int i = 0; i < vect.size(); ++i) {
    if (vect.at(i) % 2 == 0)
      even_values.push_back(vect.at(i));
  }
 
  std::cout << "Even values found: " << std::endl;
  for (unsigned int i = 0; i < even_values.size(); ++i) {
    std::cout << even_values.at(i) << std::endl;
  }
}

This example focuses on iterating over the characters comprising an input string and making decisions based on those individual characters to formulate a new string through string concatenation. Specifically, we will build a new string revised containing the same characters as the input string minus any period punctuation marks.

std::string input = "Howdy world.";

std::string revised;
for(unsigned int i = 0; i < input.size(); ++i) {
  switch(input.at(i)) {
    case '.' :
      break;
    default :
      revised += input.at(i);
  }
}

std::cout << "input: " << input << std::endl;
std::cout << "revised: " << revised << std::endl;