solution of https://algospot.com/judge/problem/read/ENCRYPT

encrypt.cpp

//https://algospot.com/judge/problem/read/ENCRYPT

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

using namespace std;

string encryptString(const string &str) {
  int length = str.length();
  string encryptedStr;

  vector<string> v;
  for (int i = 0; i < length; i += 2) {
    v.push_back(str.substr(i, 1));
  }

  for (int i = 1; i < length; i += 2) {
    v.push_back(str.substr(i, 1));
  }

  for (vector<string>::iterator it = v.begin(); it != v.end(); it++) {
    encryptedStr += *it;
  }

  return encryptedStr;
}

int main(void) {
  int testCount, i;
  string str;
  vector<string> v;
  cin >> testCount;
  for (i = 0; i < testCount; i++) {
    cin >> str;
    if (str.length() > 100)
      return 1;
 
    v.push_back(encryptString(str)); 
  }

  for (vector<string>::iterator it = v.begin(); it != v.end(); it++) {
    cout << *it << endl;
  }
  return 0;
}