HackerRank•Apr 22, 2025

Palindrome Index

Hazrat Ali

HackerRank

Given a string of lowercase letters in the range ascii[a-z], determine the index of a character that can be removed to make the string a palindrome. There may be more than one solution, but any will do. If the word is already a palindrome or there is no solution, return -1. Otherwise, return the index of a character to remove.

Example

Either remove 'b' at index  or 'c' at index .

Function Description

Complete the palindromeIndex function in the editor below.

palindromeIndex has the following parameter(s):

  • string s: a string to analyze

Returns

  • int: the index of the character to remove or 

Input Format

The first line contains an integer , the number of queries.
Each of the next  lines contains a query string .

Constraints

  • All characters are in the range ascii[a-z].

Sample Input

STDIN   Function
-----   --------
3       q = 3
aaab    s = 'aaab' (first query)
baa     s = 'baa'  (second query)
aaa     s = 'aaa'  (third query)

Sample Output

3
0
-1

Explanation

Query 1: "aaab"
Removing 'b' at index  results in a palindrome, so return .

Query 2: "baa"
Removing 'b' at index  results in a palindrome, so return .

Query 3: "aaa"
This string is already a palindrome, so return . Removing any one of the characters would result in a palindrome, but this test comes first.

Note: The custom checker logic for this challenge is available

 

Solution

#include <bits/stdc++.h>

using namespace std;

string ltrim(const string &);
string rtrim(const string &);

/*
 * Complete the 'palindromeIndex' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts STRING s as parameter.
 */

int palindromeIndex(string s)
{
    int i = 0, j = s.size() - 1;
    int stored_i = i, stored_j = j;
    bool error = false;

    if (s.size() >= 3)
    {
        while (i <= j)
        {
            if (s[i] != s[j])
            {

                if (error) return stored_j;
                error = true;
                stored_i = i;
                stored_j = j;
                i++;
            }
            else
                i++, j--;
        }

    }
    return error ? stored_i : -1;


}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string q_temp;
    getline(cin, q_temp);

    int q = stoi(ltrim(rtrim(q_temp)));

    for (int q_itr = 0; q_itr < q; q_itr++)
    {
        string s;
        getline(cin, s);

        int result = palindromeIndex(s);

        fout << result << "\n";
    }

    fout.close();

    return 0;
}

string ltrim(const string &str)
{
    string s(str);

    s.erase(
        s.begin(),
        find_if(s.begin(), s.end(), not1(ptr_fun<int, int>(isspace)))
    );

    return s;
}

string rtrim(const string &str)
{
    string s(str);

    s.erase(
        find_if(s.rbegin(), s.rend(), not1(ptr_fun<int, int>(isspace))).base(),
        s.end()
    );

    return s;
}

 

 

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