C++ Terminate has called after throwing an instance of 'std::out_of_range'

Question

I have tried countless times to solve this and nothing on the internet is helping. I've figured that the problem is with the "getline(cin,strg);" but i dont know what, the program runs perfectly if I just use "cin >> strg;", however, i want to account for spaces and whatnot. What is the problem?

#include <iostream>
#include <stdlib.h>
using namespace std;

string alphabet = "abcdefghijklmnopqrstuvwxyza";
string alphacap = "AbcdEfghIjklmnOpqrstUvwxyzA";
int loc;

string code(string str) {
    for(int i = 0; i <= str.length()-1; i++){
        if(alphabet.find(str[i]) != str.npos){
            loc = alphabet.find(str[i]);
            str = str.substr(0,i) + alphacap[loc+1] + str.substr(i+1,str.length());
        }
    }
    return str;
}

string decode(string str) {
    for(int i = 0; i <= str.length()-1; i++){
        if(alphabet.find(str[i]) != str.npos){
            loc = alphabet.find(str[i]);
            str = str.substr(0,i) + alphacap[loc-1] + str.substr(i+1,str.length());
        }
    }
    return str;
}


int main() {
    string codc;
    do{
        system("cls");
        cout << "Code or Decode? ";
        cin >> codc;
    }while(codc != "code" and codc != "Code" and codc != "decode" and codc != "Decode");

    string str;

    if(codc == "code" or codc == "Code"){
        string strg;
        getline(std::cin,strg);
        cout << code(strg);
    }else{
        string strg;
        getline(cin,strg);
        cout << decode(strg);
    }

}

What to do you want to count? Also, which is the input you are giving? — gsamaras
– gsamaras, Commented Feb 6, 2016 at 19:07

Community · Accepted Answer · 2017-05-23 11:59:14Z

0

The exception is caused by:

str.substr(i + 1, str.length());

as it tries to access str's elements up to i + str.length(). This fails for i > 0. See the original Q&A.

^{str.substr(i + 1, str.length() - i - 1); would correct it.}

If you want to get the part of the string on the right of the index i, you can just leave out the second argument:

str.substr(i + 1);

See the reference.

And this is dangerous too:

alphacap[loc + 1]
alphacap[loc - 1]

What if loc is the index of the first/last element in alphacap?

edited May 23, 2017 at 11:59

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answered Feb 6, 2016 at 19:15

LogicStuff

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4 Comments

Deck Over a year ago

I fixed what you said the problem was and it's still giving me trouble. Why does it work when i use "cin >> strg"?

LogicStuff Over a year ago

@Deck I can't say without knowing what the input is in both cases.

Deck Over a year ago

every input seems to work. Lets just say it's "Hello world"

LogicStuff Over a year ago

@Deck Your code obviously can't handle spaces. It requires each character be a letter.

Roman Bronshtein · Accepted Answer · 2016-02-06 21:40:25Z

0

After getline(std::cin,strg) strg=="".
In loop:

for(int i = 0; i <= str.length()-1; i++)

comparison <= not work correct if str.length() ==0.
After changing to

for(int i = 0; i <= (int)str.length()-1; i++)

program not fail.

Preferable also change cin >> codc; to getline(cin,codc);

Now program not fail.

answered Feb 6, 2016 at 21:40

Roman Bronshtein

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