leetcode_string_problem.cpp

https : // leetcode.com/problems/remove-all-adjacent-duplicates-in-string/description/

        class Solution
{
public:
    string removeDuplicates(string s)
    {
        string ans = "";
        int index = 0;

        while (index < s.length())
        {
            // same
            // ans ka rightmost character and string s ka current character
            if (ans.length() > 0 && ans[ans.length() - 1] == s[index])
            {
                // pop from ans string
                ans.pop_back();
            }
            else
            {
                // push
                ans.push_back(s[index]);
            }
            index++;
        }
        return ans;
    }
};

https : // leetcode.com/problems/remove-all-occurrences-of-a-substring/

        class Solution
{
public:
    string removeOccurrences(string s, string part)
    {

        while (s.find(part) != string::npos)
        {
            // if inside loop, it means that part exists in s string
            s.erase(s.find(part), part.length());
        }
        return s;
    }
};

https : // leetcode.com/problems/valid-palindrome-ii/

        class Solution
{
public:
    bool checkPalindrome(string s, int i, int j)
    {
        while (i <= j)
        {
            if (s[i] != s[j])
            {
                return false;
            }
            else
            {
                i++;
                j--;
            }
        }
        return true;
    }

    bool validPalindrome(string s)
    {
        int i = 0;
        int j = s.length() - 1;

        while (i <= j)
        {
            if (s[i] == s[j])
            {
                i++;
                j--;
            }
            else
            {
                // s[i]!=s[j]
                // 1 removal allowed
                // check plaindrome for remaining string after removal

                // ith character -> remove
                bool ans1 = checkPalindrome(s, i + 1, j);
                // jth character -> remove
                bool ans2 = checkPalindrome(s, i, j - 1);

                return ans1 || ans2;
            }
        }
        // agar yha tk pohoche ho
        // iska matlab valid palindrome hai
        // iska matlab -> 0 removal
        return true;
    }
};

https : // leetcode.com/problems/palindromic-substrings/

        class Solution
{
public:
    int expand(string s, int i, int j)
    {
        int count = 0;

        while (i >= 0 && j < s.length() && s[i] == s[j])
        {
            count++;
            i--;
            j++;
        }
        return count;
    }
    int countSubstrings(string s)
    {
        int totalCount = 0;
        for (int i = 0; i < s.length(); i++)
        {
            // ODD
            int j = i;
            int oddKaAns = expand(s, i, j);
            // EVEN
            j = i + 1;
            int evenKaAns = expand(s, i, j);
            totalCount = totalCount + oddKaAns + evenKaAns;
        }
        return totalCount;
    }
};