algorithm - C++: Implementing merge sort from scratch -


i trying test self , wanted write mergesort, without looking code online, , in time period. stuck @ point cannot understand doing wrong, since merge sort, as remember, divide strings point string 1 character , later on merge them together. code i've written below tries exact thing. wondering whether got concept wrong, or my implementation?

string merge(string str1, string str2) {   string final = "";   int = 0, j = 0;   bool fromstr1 = false;    while(true) {     if(str1[i] < str2[j]) {       final += str1[i];       i++;       if(i == str1.size()) {         break;       }     }     else {       final += str2[j];       j++;       if(j == str2.size()) {         break;         fromstr1 = true;       }     }   }    if(fromstr1) {     for(int t = i; t < str1.size(); t++) {       final += str1[t];     }   }   else {     for(int t = j; t < str2.size(); t++) {       final += str2[t];     }   }    return final; }  string mergesort(string str1, int start, int end) {   if(end - start == 1)     return str1;   else {     int pivot = (end - start) / 2;     string newstr1 = mergesort(str1, start, pivot);     string newstr2 = mergesort(str1, pivot + 1, end);     return merge(newstr1, newstr2);   } }

note changes:

#include <iostream> #include <string>  using namespace std;  string merge(string str1, string str2) {   string final = "";   int = 0, j = 0;   bool fromstr1 = false;    while (true) {     if (i >= (int)str1.size()) {       break;     }     if (j >= (int)str2.size()) {       fromstr1 = true; // changed order of break!       break;     }      if (str1[i] < str2[j]) {       final += str1[i];       i++;     }     else {       final += str2[j];       j++;     }   }    if (fromstr1) {     (int t = i; t < (int)str1.size(); t++) {       final += str1[t];     }   }   else {     for(int t = j; t < (int)str2.size(); t++) {       final += str2[t];     }   }    return final; }  string mergesort(string str1) {   int len = str1.size();   if (len <= 1)     return str1;   else {     string newstr1 = mergesort(str1.substr(0, len / 2));     string newstr2 = mergesort(str1.substr(len / 2, len - len / 2));     return merge(newstr1, newstr2);   } }  int main() {   cout << '"' << mergesort("") << '"' << endl;   cout << '"' << mergesort("a") << '"' << endl;   cout << '"' << mergesort("ba") << '"' << endl;   cout << '"' << mergesort("132") << '"' << endl;   cout << '"' << mergesort("4321") << '"' << endl;   cout << '"' << mergesort("54321") << '"' << endl;   return 0; }

output (ideone):

"" "a" "ab" "123" "1234" "12345"

Comments

Post a Comment

Popular posts from this blog

Why does Ruby on Rails generate add a blank line to the end of a file? -

running rails generate controller foo home results in: class foocontroller < application controller def home end end (there's nothing on line in actual file, blank line) is there purpose blank line? it's common use newline indicate end of line, last line. many editors (like vi, use) add in newline silently. consensus text files (especially in unix world) should end in newline, , there have been problems historically if wasn't present. why should text files end newline? the tool used count lines in file "wc" counts newlines in file, without trailing newline show 3 instead of 4. it improves readability of templates used in generator. consider: https://github.com/rails/rails/blob/master/railties/lib/rails/generators/rails/controller/templates/controller.rb to remove trailing newline, template have last line of: end<% end -%> instead of: end <% end -%> that seems less readable me. the discussion below refers ...
Read more

keyboard - Smiles and long press feature in Android -

i've created android keyboard. how add features inserting smilies, , using long keypresses display symbols? to create long-press behavior allows select several options pop-up menu, follow guide (specifically pop-up menu section): http://developer.android.com/guide/topics/ui/menus.html smileys (also known emoticons) combination of keys, understood programs , parsed same way. have do, when clicks smiley face on keyboard, simulate pressing of key combination matching emoticon. example, when clicks smiley, should simulate key presses ':' , ')' :). here's list of emoticons: http://en.wikipedia.org/wiki/list_of_emoticons
Read more

node.js - Bad Request - node js ajax post -

i'm using express 3.0 , node v0.11.0. have button submits form , i'm using ajax post data json object node server. client code is: $('#contact').submit(function(e) { console.log('submit called'); var formdata = json.stringify($('form').serializeobject()); console.log(formdata); $.ajax({ url: "http://localhost:3000/savedata/", type: "post", datatype: 'json', data: {objectdata: formdata}, contenttype: "application/json", complete: function() { console.log('process complete'); }, success: function(data) { console.log('process sucess'); }, error: function() { console.log('process error'); }, }); return false; }); then on server: var express = require('express'); var app = express(); app.set('views', __dirname + '/views'); app.set('view engine', 'jade'); app.use(express.bodyparser());...
Read more