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#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <cstring>
using namespace std;
const int ARRAYSIZE = 128;
void characterCount(char ch, int list[]);
void calcShift( int& shift, int list[]);
void writeOutput(ifstream &in, ofstream &out, int shift);
int main()
{
int asciiCode = 0,
shift = 0;
char ch;
string inputFileName;
ifstream inputFile;
ofstream outputFile;
string reply;
//Open input file
cout << "Input file name: ";
getline(cin, inputFileName);
inputFile.open(inputFileName.c_str());
if (!inputFile.is_open()) {
cout << "Unable to open file or it doesn't exist." << endl;
return 1;
}
//output file
cout << "Output file name: ";
getline(cin, inputFileName);
outputFile.open(inputFileName.c_str());
int list[ARRAYSIZE] = {0};
while (inputFile.peek() != EOF)
{
inputFile.get(ch);
characterCount(ch, list);
}
inputFile.clear();
inputFile.seekg(0);
calcShift (shift, list); //Calculate the shift based on the characters counted
writeOutput(inputFile, outputFile, shift); //Decypher and write to the other document
inputFile.close();
outputFile.close();
cout << "Press enter to continue...";
getline(cin, reply);
return 0;
}
void characterCount(char ch, int list[])
{
if (ch >= 'A' && ch <= 'z') //If the character is in the alphabet...
{
int asciiCode = 0;
asciiCode = (ch); //Change it to the ASCII number
list[asciiCode]++; //And note it on the array
}
}
void calcShift( int& shift, int list[])
{
int maxIndex = 0; //Asuming that list[0] is the largest
int mostFreqLetter;
for (int i = 1; i < ARRAYSIZE; i++)
{
if (list[maxIndex] < list[i])
maxIndex = i; //If this is true, change the largest index
}
if (maxIndex >= 'A' && maxIndex <= 'Z') //Calculate shift for for upper-case letters
shift = 'E' - maxIndex;
if (maxIndex >= 'a' && maxIndex <= 'z') //For lower-case letters
shift = 'e' - maxIndex;
mostFreqLetter = 'e' - shift;
cout << "Most frequent letter is " << shift << endl;
cout << "Most is " << mostFreqLetter << endl;
}
void writeOutput(ifstream &inputFile, ofstream &outputFile, int shift)
{
char ch;
while (inputFile.peek() != EOF) { //Until it is the end of the file...
inputFile.get(ch); //Get the next character
if (ch >= 'A' && ch <= 'Z') //If the character is in the alphabet...
{
ch = 'A' + (((ch - 'A') + shift + 26) % 26);
}
if (ch >= 'a' && ch <= 'z') //If the character is in the alphabet...
{
ch = 'a' + (((ch - 'a') + shift + 26) % 26);
}
outputFile << ch; //Print to the outfile
}
}
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