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mandliyamandliya
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Day-9 removing duplicates from a string
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‎README.md

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This repository will contain random algorithm and data structure problems I resolve to solve at least one a day.
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## Current Streak
5-
8 days, longest streak ( 8 days ) as of August 24, 2015.
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9 days, longest streak ( 9 days ) as of August 25, 2015.
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## Include Directiory
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Include directory and sub directories contain STL like header file implementation of various algorithms and data structures. Following header only implementation,
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- Problem 1 : Determine if a string has unique chars.
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- Problem 2 : (Edition 5) Reverse a c-string.
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- Problem 2 : (Edition 6) Determine if two string are permutations of each other.
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- Problem 3 : (Edition 5) Remove duplicate chars from a string

‎cracking_the_coding_interview_problems/1-2-edi5-reverseString.cpp

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/*
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* Cracking the coding interview edition *5* old one
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* 1.2 Reverse a string when you are a pass a null terminated C string.
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*/
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#include<iostream>
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#include<cstring>
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#include<generic.h>
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void reverse1( char * str)
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{
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int len = std::strlen(str);
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for ( int i = 0; i < len/2; ++i ) {
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algo::swap( str[i], str[len - i - 1] );
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}
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}
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void reverse2( char *str ) {
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if ( !str )
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return;
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char *p = str;
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char *q = str;
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while (*q) ++q;
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--q;
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//q now points to last char and p points to first char
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while ( p < q )
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std::swap( *p++, *q-- );
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}
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int main()
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{
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char str[] = "abcdefghijklmnopqrstuvwxyz";
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reverse1(str);
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std::cout << "On reversing it once: " << str << std::endl;
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reverse2(str);
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std::cout << "On reversing it again: " << str << std::endl;
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return 0;
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}

‎cracking_the_coding_interview_problems/1-3-edi5-removeDuplicates.cpp

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/*
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* Cracking the coding interview, edition 5
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* Problem 1.3
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* Write an algorithm to remove duplicate chars from a string
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*/
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#include <iostream>
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#include <cstring>
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using std::string;
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using std::cin;
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using std::cout;
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using std::endl;
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/*
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* Function - removeDuplicates1
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* Args - A string
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* Return - Arg string with no duplicate chars
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* Runtime - O(n)
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* Assumption - contains letter ( a - z )
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*/
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string removeDuplicates1( const string & str )
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{
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int len = str.length();
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if ( len < 2 ) {
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return str;
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}
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int check = 0;
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string result("");
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for ( auto & ch : str ) {
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int c = (int)( ch - 'a');
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if ( (check & ( 1 << c )) == 0) {
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result += ch;
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check |= ( 1 << c);
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}
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}
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return result;
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}
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/*
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* Function - removeDuplicates2
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* Args - A string
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* Return - Arg string with no duplicate chars
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* Runtime - O(n)
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* Assumption - ASCII extended char set
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*/
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string removeDuplicates2 ( const string & str )
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{
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int len = str.length();
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if ( len < 2 )
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return str;
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string result("");
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bool check[256];
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for ( auto & ch : str ) {
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if ( !check[(int)ch] ) {
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check[(int)ch] = true;
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result += ch;
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}
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}
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return result;
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}
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/*
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* Function - removeDuplicates3
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* Args - A string
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* Return - Arg string with no duplicate chars
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* Runtime - O(n^2)
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* Assumption - NONE
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*/
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string removeDuplicates3( string str )
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{
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int len = str.length();
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if ( len < 2 ) {
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return str;
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}
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string result("");
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for ( int i = 0; i < len; ++i) {
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if ( str[i] != '\0' ) {
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result += str[i];
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for ( int j = i + 1; j < len; ++j ) {
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if ( str[i] == str[j] ) {
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str[j] = '\0';
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}
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}
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}
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}
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return result;
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}
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/*
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* Function - removeDuplicates4
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* Args - A C string
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* Return - void, we change the char array we pass as arg
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* Runtime - O(n)
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* Assumption - contains letter ( a - z )
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*/
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void removeDuplicates4( char * str )
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{
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int len = std::strlen(str);
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if ( len < 2) {
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return;
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}
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int check = 0;
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int cindx = 0;
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for ( int i = 0; i < len; ++i) {
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int c = (int) ( str[i] - 'a');
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if ( (check & ( 1 << c )) == 0 ) {
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str[cindx++] = str[i];
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check |= ( 1 << c );
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}
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}
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str[cindx] = '\0';
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}
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/*
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* Function - removeDuplicates5
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* Args - A c string
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* Return - void, we change the c-string we pass to function
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* Runtime - O(n^2)
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* Assumption - NONE
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*/
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void removeDuplicates5( char * str )
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{
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int len = std::strlen(str);
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if ( len < 2 ) {
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return;
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}
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int idx = 0;
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for ( int i = 0; i < len; ++i) {
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if ( str[i] != '\0' ) {
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str[idx++] = str[i];
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for ( int j = i + 1; j < len; ++j ) {
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if ( str[i] == str[j] ) {
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str[j] = '\0';
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}
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}
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}
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}
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}
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/*
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* Function - removeDuplicates6
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* Args - A c string
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* Return - void, we change the c-string we pass to function
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* Runtime - O(n)
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* Assumption - ASCII extended char set
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*/
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void removeDuplicates6 ( char *str )
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{
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int len = std::strlen(str);
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if ( len < 2 )
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return;
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bool check[256] = {false};
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int idx = 0;
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for ( int i = 0; i < len; ++i )
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{
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if ( !check[(int)str[i]] ) {
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check[(int)str[i]] = true;
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str[idx++] = str[i];
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}
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}
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str[idx] = '\0';
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}
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int main()
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{
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string str1("aaaabbbbbcddeffgheee");
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string str2("abcd");
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string str3("a");
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string str4("");
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cout << "For method 1:" << endl;
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cout << "original-string:" << str1 << " after removing duplicates:" << removeDuplicates1(str1) << endl;
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cout << "original-string:" << str2 << " after removing duplicates:" << removeDuplicates1(str2) << endl;
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cout << "original-string:" << str3 << " after removing duplicates:" << removeDuplicates1(str3) << endl;
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cout << "original-string:" << str4 << " after removing duplicates:" << removeDuplicates1(str4) << endl;
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cout << "\n\nFor method 2:" << endl;
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cout << "original-string:" << str1 << " after removing duplicates:" << removeDuplicates2(str1) << endl;
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cout << "original-string:" << str2 << " after removing duplicates:" << removeDuplicates2(str2) << endl;
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cout << "original-string:" << str3 << " after removing duplicates:" << removeDuplicates2(str3) << endl;
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cout << "original-string:" << str4 << " after removing duplicates:" << removeDuplicates2(str4) << endl;
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cout << "\n\nFor method 3:" << endl;
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cout << "original-string:" << str1 << " after removing duplicates:" << removeDuplicates3(str1) << endl;
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cout << "original-string:" << str2 << " after removing duplicates:" << removeDuplicates3(str2) << endl;
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cout << "original-string:" << str3 << " after removing duplicates:" << removeDuplicates3(str3) << endl;
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cout << "original-string:" << str4 << " after removing duplicates:" << removeDuplicates3(str4) << endl;
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cout << "\n\nFor method 4:" << endl;
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char str5[] = "aaaabbbbcccc";
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char str6[] = "abcde";
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char str7[] = "a";
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char str8[] = "";
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cout << endl;
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cout << "original-string:" << str5 << " after removing duplicates:";
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removeDuplicates4(str5);
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cout << str5 << endl;
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cout << "original-string:" << str6 << " after removing duplicates:";
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removeDuplicates4(str6);
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cout << str6 << endl;
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cout << "original-string:" << str7 << " after removing duplicates:";
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removeDuplicates4(str7);
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cout << str7 << endl;
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cout << "original-string:" << str8 << " after removing duplicates:";
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removeDuplicates4(str8);
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cout << str8 << endl;
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cout << "\n\nFor method 5:" << endl;
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char str9[] = "aaaabbbbccccdddeeefffaaabbb";
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char str10[] = "abcdef";
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char str11[] = "b";
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char str12[] = "";
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cout << endl;
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cout << "original-string:" << str9 << " after removing duplicates:";
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removeDuplicates5(str9);
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cout << str9 << endl;
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cout << "original-string:" << str10 << " after removing duplicates:";
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removeDuplicates5(str10);
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cout << str10 << endl;
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cout << "original-string:" << str11 << " after removing duplicates:";
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removeDuplicates5(str11);
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cout << str11 << endl;
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cout << "original-string:" << str12 << " after removing duplicates:";
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removeDuplicates5(str12);
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cout << str12 << endl;
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cout << "\n\nFor method 6:" << endl;
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char str13[] = "aaaabbbbccccdddeeefffaaabbb";
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char str14[] = "abcdef";
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char str15[] = "b";
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char str16[] = "";
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cout << endl;
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cout << "original-string:" << str13 << " after removing duplicates:";
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removeDuplicates6(str13);
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cout << str13 << endl;
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cout << "original-string:" << str14 << " after removing duplicates:";
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removeDuplicates6(str14);
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cout << str14 << endl;
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cout << "original-string:" << str15 << " after removing duplicates:";
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removeDuplicates6(str15);
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cout << str15 << endl;
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cout << "original-string:" << str16 << " after removing duplicates:";
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removeDuplicates6(str16);
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cout << str16 << endl;
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cout << endl;
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return 0;
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}

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