How to fix output from repeating cout from IF/ELSE statments - c++

Question

I have a completed code for my class; it creates a randomized string based on how many characters that the user asks for, and it then allows for the user to specify if they want to find a particular pair of characters in the string. That last part is based on a if/else statement that either gives the location, or is suppose to tell them there is no pair in the string.
My issue is that, when given a pair to find, if its in the string it gives the corrected statement, however, it also gives the else statement, repeated several times. if the pair is not in the string, it then gives the correct else statement, but repeats the cout several times. I don't know how to solve this issue.
Here is my code and screen shots of my outputs.
#include <iostream>
#include <stdlib.h>
#include <time.h>
using namespace std;
int main() {
int i=0, n;
char alphabet[26];
char RandomStringArray [100];
char Ltr1, Ltr2;
srand(time(0));
cout <<"How many letters do you want in your random string (no less than 0, no more than 100): ";
cin >> n;
for (int i=0; i<=25; i++)
alphabet[i] = 'a' + i;
while(i<n) {
int temp = rand() % 26;
RandomStringArray[i] = alphabet[temp];
i++;
}
for(i=0; i<n; i++)
cout<<RandomStringArray[i];
cout<<"\n";
cout<<"What letter pair would you like to find? ";
cin>>Ltr1>>Ltr2;
for (i=0; i<n; i++)
if (Ltr1==RandomStringArray[i] && Ltr2== RandomStringArray[i+1]){
cout<<"The pair is in the string starting at character number "<<i+1<<" in the string. \n";
}
else if (Ltr1!=RandomStringArray[i] && Ltr2!= RandomStringArray[i+1])
cout<<"no";
return 0;
}

Answer 1

Your final for loop is looping through every character in the random string from begin to end, which is fine for searching, but it is outputting the result of comparing every character, which is not what you want. Don't display any output at all until the loop is finished, eg:
for (i = 0; i < (n-1); i++)
{
if (RandomStringArray[i] == Ltr1 && RandomStringArray[i+1] == Ltr2)
break;
}
if (i < (n-1))
cout << "The pair is in the string starting at character number " << i+1 << " in the string.\n";
else
cout << "The pair is not found in the string.\n";
I would suggest wrapping the search in a function, eg:
int findPair(const char *str, int len, char Letter1, char Letter2)
{
for (i = 0; i < (len-1); i++)
{
if (str[i] == Letter1 && str[i+1] == Letter2)
return i;
}
return -1;
}
...
i = findPair(RandomStringArray, n, Ltr1, Ltr2);
if (i != -1)
cout << "The pair is in the string starting at character number " << i+1 << " in the string.\n";
else
cout << "The pair is not found in the string.\n";
That being said, since you are using C++ anyway, you should go full C++, not a mix of C and C++, eg:
#include <iostream>
#include <string>
#include <random>
#include <algorithm>
int main() {
int n;
char alphabet[26];
std::string RandomString;
char LtrPair[2];
std::generate(std:begin(alphabet), std::end(alphabet), [ch = 'a'] () mutable { return ch++; } );
std::cout << "How many letters do you want in your random string: ";
std::cin >> n;
std::random_device rd;
std::mt19937 gen(rd());
std::uniform_int_distribution<> dis(0, 25);
RandomString.resize(n);
std::generate(RandomString.begin(), RandomString.end(), [&](){ return alphabet[dis(gen)]; };
std::cout << RandomString << "\n";
std::cout << "What letter pair would you like to find? ";
cin >> LtrPair[0] >> LtrPair[1];
auto pos = RandomString.find(LtrPair, 0, 2);
if (pos != std::string::npos)
std::cout << "The pair is in the string starting at character number " << pos+1 << " in the string.\n";
else
std::cout << "The pair is not found in the string.\n";
return 0;
}

Answer 2

Since you have placed your if...else construct inside of a for loop, it is evaluated every time. This means that for every instance where the first condition isn't true, the else clause is executed, causing your "no" message to repeat.