palindrome.cpp

// first take out all the spaces and punctuation from the sentence
// do I also need to convert caps to lowercase?
// compute midpoint
// check to make sure letters that are equidistant from the midpoint are the same
// do this slightly differently depending on whether the number of characters is even or odd

#include <string>

class Solution {
public:
    bool isPalindrome(string s) {
        string onlyLetters;
        onlyLetters = rem_stuff(s);
        int l = onlyLetters.length();
        if(l == 1){
            return true;
        }
        int low_indx, high_indx;
        if (l%2 == 0){
            high_indx = l/2;
            low_indx = high_indx - 1;
        }
        else{
            low_indx = l/2 - 1;
            high_indx = l/2 + 1;
        }

        // at this point all phrases are at least 2 characters long
        do{
            if(onlyLetters[low_indx]==onlyLetters[high_indx]){
                --low_indx;
                ++high_indx;
            }
            else{
                return false;
            }
        }while(low_indx>=0);
        return true;
    }

    string rem_stuff(string s){
        int stl = s.length(); //compute length of incoming string only once;
        string f = s; // set it equal to s then take out spaces and punctuation
        int findx = 0;
        for(int i=0; i<s.length(); i++){
            if(ispunct(s[i])||isdigit(s[i])||isspace(s[i])){
                //if it's any of those things remove it and continue to next
                // actually, should keep the digit option?
                f.erase(findx, 1);
                // don't update findx becasue now that index contains the next value
            }
            else{
                f[findx]=tolower(f[findx]);  // can I do this if digits are an option?
                ++findx;
                //update findx every time a character is one I want to keep
            }
        }
        return f;
    }
};