ETH_Informatik/Informatik_I/Exercise_6/Task_2

Task 2: Number of Occurrences

• Task
• Input
• Output
• Reminder - How to use vector
• Solution

Task

Write a program using a vector to perform the following:

1. Read integer values from standard input and insert them in a vector until a negative integer is encountered;
2. Read an extra non-negative integer n;
3. Output the number of occurrences of n encountered during phase (1).

Your solution must split the sub-tasks of the program (reading the vector, counting the occurrences, and maybe other sub-tasks) into separate functions. Those functions must use the proper reference parameters to access the vector.

Note: we consider solutions as incorrect if they use library functions (or data structures) beyond the ones discussed in the lectures so far to perform the actual computation.

Input

A sequence of of integer values containing a single negative integer, in penultimate position.

Example:

0 1 1 2 3 5 8 13 21 -1 1

Output

The number of occurrences of the last integer in the sequence before the negative integer.

Example: for the input given above, the number of occurrences of 1 before -1 occurs is

2

Reminder - How to use vector

To define a vector (for example of integer numbers), you can use the following constructor

std::vector<int> my vec = std::vector<int>(length, init_value);

You can insert element at the back of the vector with:

my_vec.push_back(number);

To access the elements of the vector you have to use the random access ([]) operator:

std::cout << "First element: " << my_vec[0];

Solution

#include <iostream>
#include <vector>

void readvec(std::vector<int>& vec, int& num) {
  vec.push_back(num);
}

int occvec(std::vector<int>& vec, int& num, int& count) {
  for (unsigned long i = 0; i < vec.size(); ++i) {
    if (vec[i] == num)
      ++count;
  }
  return count;
}

int main() {

  int i;
  int con;
  int count = 0;
  std::vector<int> vec;

  std::cin >> i;

  while (i >= 0) {
    readvec(vec, i);
    std::cin >> i;
  }

  std::cin >> con;

  occvec(vec, con, count);

  std::cout << count;

  return 0;
}

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Made by JirR02 in Switzerland 🇨🇭