#include<iostream>
#include<vector>
#include<stdlib.h>
#include <stdexcept>
#include <fstream>
#include <string>
#include <algorithm>
#include <stddef.h>

using namespace std;

void changeuppercase(vector<char>& word, int size)
{
for (int i = 0; i < size; i++)
{
if (word[i] >= 97 && word[i] <= 122)
word[i] -= 32;
}
}
void printtext(vector<char> word, int size)
{
for (int i = 0; i < size; i++)
{
cout << (char)(word[i] + 65);
}
cout << endl;
return;
}
size_t getinput(vector<char>& sen)
{
char b;
while (1)
{
b = getchar();
if (b == '\n')
break;
sen.push_back(b);
}
return sen.size();
}
int main()
{
vector<char> sen;
vector<char> enc_sen;
vector<char> dec_sen;
int *p;
int j;
size_t size;
cout << "Enter Message to Encrypt:";
size = getinput(sen);
changeuppercase(sen, size);
p = (int*)malloc(sen.size() * sizeof(int));
for (j = 0; j < size; j++)
{
p[j] = rand() % 26;
if (sen[j] >= 65 && sen[j] <= 90)
enc_sen.push_back((char)((sen[j] - 65 + p[j]) % 26));
else if (sen[j] >= 97 && sen[j] <= 122)
enc_sen.push_back((char)((sen[j] - 97 + p[j]) % 26));
else
enc_sen.push_back((char)sen[j]);
}
cout << "\nEncoded Message:";
printtext(enc_sen, size);
cout << "\nKey for decryption:\n";
for (j = 0; j < size; j++)
{
cout << (char)(p[j] + 65);
}
cout << endl;
cout << "\nDecrypted Message:";
for (j = 0; j < size; j++)
{
if ((enc_sen[j] - p[j]) < 0)
dec_sen.push_back((char)(enc_sen[j] - p[j] + 26));
else if ((enc_sen[j] - p[j]) >= 0)
dec_sen.push_back((char)(enc_sen[j] - p[j]));
else
dec_sen.push_back((char)enc_sen[j]);
}
printtext(dec_sen, size);
return 0;
}