An approach to Programming Contests with C++
- 2. A lil Bit About Templates B4 V Begin So, What Are They ??? It Aids Generic Programming ( Basically, Makes Life Much Easier ) You Can Create a Queue Of Type T where, T is of any type !!! Eg. queue<int> iq; queue<string> sq;
- 3. File Handling Handling Input, Output From Files Is Much Easier Than You Think !!! freopen(“input file name”,”r”,stdin); freopen(“output file name”,”w”,stdout);
- 4. - TIP - string s; getline(cin , s , '\n'); Use this to read a whole line of text from the input file
- 5. A world of strings
- 6. Find Simplest way to find a substring What Does It Do ? Returns The Index Of The First Occurrence Of The Substring. If There Is No Such Occurrence, returns a value > Length Of String. string a=“hello world”; cout<<a.find(“0 w”);
- 7. Replace An Easy Way To Replace Text In Strings What Does It Do ? Replaces Some Particular Text In A String With The Text You Want To Replace With string a=“hello world”; cout<<a.replace(i,j,”hi”);
- 8. Other Useful String Functions string s=“01236789876543210”; s.insert(i,”45”); s.erase(i,j); s.length(); s.rfind(“3”);
- 9. Extract Data From A String With sscanf() It is like scanf() but, scans from a string instead of standard input !!! string s=“12:40”; int h,m; sscanf(s.c_str() , "%d:%d“ , &h , &m); cout<<h<<endl<<m;
- 10. - TIP - You can use find and replace together, to replace all occurences of a particular substring in a string, with some other sequence of characters, irrespective of the size of the new sequence of characters ! Very Useful !!!
- 12. Converting Anything Printable, To A String Not as hard as it sounds !! stringstream ss; string s; float f=1.732; int i=43; char c=‘g’; ss<<“StringstreamsRock!!”<<f<<i<<c; ss>>s; cout<<s;
- 13. - TIP - It Is A Better Idea To Use-- getline(ss , s , ‘\n’); (or) s=ss.str();
- 15. a^=b^=a^=b; What Does It Do ?? Guesses Permitted !!
- 16. a=a^b; b=a^b; a=a^b; After Simplifying It A Little Bit
- 17. It Works Coz Of The Fact That: a^b=c => b^c=a c^a=b
- 18. #include<vector>
- 19. Capabilities: Easy Sorting!! Constant Access Time!! Linear Time for finding elements!!
- 20. So why not Arrays?? Variable Size!!
- 21. Useful Functions: push_back() pop_back() insert() erase() clear() assign()
- 22. Ready to use Algorithms #include<algorithm>
- 23. C++ Already Contains: (Used with respect to Vector v1) sort() stable_sort() qsort() find() reverse() merge()
- 24. There’s More.. min_element() max_element() next_permutation() prev_permutation()