C++ Simple letter to number encryption [closed] - c++

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I am very new and horrible at C++.
I was hoping someone could figure out what this error means, I seriously have no idea what to do, I am NOT asking to have you to try to make it more effiecent, I realize my uneffieceny.
I am trying to convert letters to numbers, I understand this is weak encryption.
Code:
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <algorithm>
#include <string>
using namespace std;
int main()
{
std::string ptxt = "";
string etxt = "";
cin >> ptxt;
std::replace( ptxt.begin(), ptxt.end(), 'a', '1');
std::replace( ptxt.begin(), ptxt.end(), 'b', '2');
std::replace( ptxt.begin(), ptxt.end(), 'c', '3');
std::replace( ptxt.begin(), ptxt.end(), 'd', '4');
std::replace( ptxt.begin(), ptxt.end(), 'e', '5');
std::replace( ptxt.begin(), ptxt.end(), 'f', '6');
std::replace( ptxt.begin(), ptxt.end(), 'g', '7');
std::replace( ptxt.begin(), ptxt.end(), 'h', '8');
std::replace( ptxt.begin(), ptxt.end(), 'i', '9');
std::replace( ptxt.begin(), ptxt.end(), 'j', '10');
std::replace( ptxt.begin(), ptxt.end(), 'k', '11');
std::replace( ptxt.begin(), ptxt.end(), 'l', '12');
std::replace( ptxt.begin(), ptxt.end(), 'm', '13');
std::replace( ptxt.begin(), ptxt.end(), 'n', '14');
std::replace( ptxt.begin(), ptxt.end(), 'o', '15');
std::replace( ptxt.begin(), ptxt.end(), 'p', '16');
std::replace( ptxt.begin(), ptxt.end(), 'q', '17');
std::replace( ptxt.begin(), ptxt.end(), 'r', '18');
std::replace( ptxt.begin(), ptxt.end(), 's', '19');
std::replace( ptxt.begin(), ptxt.end(), 't', '20');
std::replace( ptxt.begin(), ptxt.end(), 'u', '21');
std::replace( ptxt.begin(), ptxt.end(), 'v', '22');
std::replace( ptxt.begin(), ptxt.end(), 'w', '23');
std::replace( ptxt.begin(), ptxt.end(), 'x', '24');
std::replace( ptxt.begin(), ptxt.end(), 'y', '25');
std::replace( ptxt.begin(), ptxt.end(), 'z', '26');
return 0;
}
Build Log (Debug?)

Answer 1

Let's start from the beginning of the build log:
main.cpp|25|warning: multi-character character constant [-Wmultichar]|
A character constant is like 'a' or '1'. If we go and look at the code this warning points to we see:
std::replace( ptxt.begin(), ptxt.end(), 'l', '12');
Note that '12': there are two characters inside that character constant. This is warning you about the fact that you have more than one. What exactly a 'multi-character' character constant is and what they're good for doesn't matter, you don't need them and should not be using them.
If you really want text like "hello" to be encoded as "85121215" or "8 5 12 12 15" then you're going to have to rethink how you do the replacement. This is for two reasons: a multi-character character constant like '12' will not look like 12 in your output file, and secondly because std::replace will not handle replacing a single character like l with multiple characters.
For now lets replace all the mult-character character constants you've got with single-character versions:
std::replace( ptxt.begin(), ptxt.end(), 'a', '1');
std::replace( ptxt.begin(), ptxt.end(), 'b', '2');
std::replace( ptxt.begin(), ptxt.end(), 'c', '3');
std::replace( ptxt.begin(), ptxt.end(), 'd', '4');
std::replace( ptxt.begin(), ptxt.end(), 'e', '5');
std::replace( ptxt.begin(), ptxt.end(), 'f', '6');
std::replace( ptxt.begin(), ptxt.end(), 'g', '7');
std::replace( ptxt.begin(), ptxt.end(), 'h', '8');
std::replace( ptxt.begin(), ptxt.end(), 'i', '9');
std::replace(ptxt.begin(), ptxt.end(), 'j', 'a');
std::replace(ptxt.begin(), ptxt.end(), 'k', 'b');
std::replace(ptxt.begin(), ptxt.end(), 'l', 'c');
std::replace(ptxt.begin(), ptxt.end(), 'm', 'd');
std::replace(ptxt.begin(), ptxt.end(), 'n', 'e');
std::replace(ptxt.begin(), ptxt.end(), 'o', 'f');
std::replace(ptxt.begin(), ptxt.end(), 'p', 'g');
std::replace(ptxt.begin(), ptxt.end(), 'q', 'h');
std::replace(ptxt.begin(), ptxt.end(), 'r', 'i');
std::replace(ptxt.begin(), ptxt.end(), 's', 'j');
std::replace(ptxt.begin(), ptxt.end(), 't', 'k');
std::replace(ptxt.begin(), ptxt.end(), 'u', 'l');
std::replace(ptxt.begin(), ptxt.end(), 'v', 'm');
std::replace(ptxt.begin(), ptxt.end(), 'w', 'n');
std::replace(ptxt.begin(), ptxt.end(), 'x', 'o');
std::replace(ptxt.begin(), ptxt.end(), 'y', 'p');
std::replace(ptxt.begin(), ptxt.end(), 'z', 'q');
This change addresses all the warnings in the build log, and also happens to fix all the errors as well.
If you're curious what the errors were: they were just a sort of verbose way of telling you that your arguments to std::replace() were not correct. Multi-characters happen to have the type int instead of char, and std::replace() does not accept taking an int for the last argument when the second to last argument is a char.
this has type `int`
|
V
std::replace( ptxt.begin(), ptxt.end(), 'l', '12');
^
|
this has type `char`... mismatch error between `int` and `char`
Taking issues one at a time is a good way to avoid being overwhelmed by all of them at once. Just take them one at a time, starting from the beginning. Often fixing one issue reported earlier will make other warnings and errors go away so you never have to bother with them.
Do not ignore warnings. Even though your programs may compile and work without all the warnings being fixed, it's a bad habit to ignore them. In fact, you should enable more warnings if you can, and pay attention to those too.