More String Questions

2. Question Reverse words in a given string

Tips to solving:

• Use pointers as index placers to keep track of beginning of word and end of the word

#include<iostream>
using std::cout;
using std::endl;
#include<string>
using std::string;
#include<vector>
using std::vector;

string reverseWords(string str){

    vector<string> temp;

    // loop thru str and removed word
    int ptr0 = 0;  // track of the index
    int ptr1 = 0;   // track of length of the string

    for (int i = 0; i < str.length(); i++ )
    {
        // Start both pointers at the beginging of the loop in the string

        if (str[i] != '.')
        {
            ++ptr1;
        }   
        else {
        
            temp.push_back(str.substr(ptr0,ptr1));
            // update ptr indexes: set ptr0 to ptr
            ptr0 = i + 1;
            ptr1 = 0; // update length to zero
        }
        // add last wor
    }
    temp.push_back(str.substr(ptr0,ptr1)); // add last element
    string reverse;

    // Find Size of the temp vector
    int temp_size = temp.size()-1;

    for (int i = temp_size; i >= 0; i-- )
    {
        // add to reverse string and add "."
        reverse += temp[i];
        reverse += ".";
    }

    return reverse;

}



int main(){

    string pass = "i.like.this.program.very.much";

    cout << reverseWords(pass) << endl;

}

Output

much.very.program.this.like.i.

3. Longest Substring Without Repeating Characters

Tips for Solving

• Create a vector with known values (chars) that we’ve already found
• use a pointer value to keep track

/*
Longest Substring Without Repeating Characters!!!!!!

https://leetcode.com/problems/longest-substring-without-repeating-characters/

Example 1: 

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

    Input: s = "pwwkew"
    Output: 3
    Explanation: The answer is "wke", with the length of 3.
    Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

Example 4:

    Input: s = ""
    Output: 0


*/

#include <iostream>
using std::cout;
using std::endl;
#include<string>
using std::string;
#include<vector>
using std::vector;

string check_length(string str2 ){

    string temp;

    if (str2.length() > temp.length())
    {
        //update string
        temp = str2;
    }

     return temp;
}

string longestSubstring(string str ){
    // find longest substring
    string longest_;
    string temp_; // temp string size
    vector<bool> known_(128); // vector<bool> = <true, true, t
    int ptr0 = 0; // begin index
    
    for (int i = 0; i < str.length(); i++)
    {
        int value = str[i];

        if (known_[value]){
            // value is already in our vector so
            // add to known_ vector
           //  check_length(str.substr(ptr0, i-ptr0)); // send phrase to check (i-1) = length of substring

            temp_ = check_length(str.substr(ptr0, i-ptr0));
            if (temp_.length() > longest_.length()){
                // replace/update
                longest_ = temp_;
            }

            // Clear our Vector
            known_.clear();
            // reset postion of index
             ptr0 = i;
        }
        // else add
        known_[value] = true;
    }

    return longest_;
}

int main() {

    string phrase ="abcabcbb";
    string phrase2 = "pwwkeaighsdlmncewqw";
    string phrase3 = "bbbbbbbbbbbbbbbbbb";
    string phrase4 = "";



    string longestsub = longestSubstring(phrase);
    string longestsub2 = longestSubstring(phrase2);
    string longestsub3 = longestSubstring(phrase3);
    string longestsub4 = longestSubstring(phrase4);


    cout << "For the Phrase " << phrase <<  " ;The longest substring is: " << longestsub <<  " with the size: " << longestsub.size() <<endl;
    cout << "For the Phrase " << phrase2 << " ;The longest substring is: " << longestsub2 <<  " with the size: " << longestsub2.size() <<endl;
    cout << "For the Phrase " << phrase3 << " ;The longest substring is: " << longestsub3 <<  " with the size: " << longestsub3.size() <<endl;
    cout << "For the Phrase " << phrase4 << " ;The longest substring is: " << longestsub4 <<  " with the size: " << longestsub4.size() <<endl;
}

Output:

For the Phrase abcabcbb ;The longest substring is: abc with the size: 3
For the Phrase pwwkeaighsdlmncewqw ;The longest substring is: wkeaighsdlmnc with the size: 13
For the Phrase bbbbbbbbbbbbbbbbbb ;The longest substring is: b with the size: 1
For the Phrase  ;The longest substring is:  with the size: 0

Question Number 4 : Question: Longest Repeating Character Replacement

Tips for Solving:

• In this problem we need to..

Question NUmber 5

Question Number 6