Swype implementation in C++

swype.cpp

/*
The MIT License (MIT)
 
Copyright (c) 2013 Krishna Bharadwaj <krishna@krishnabharadwaj.info>
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
 
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/

#include <iostream>
#include <fstream>
#include <map>
#include <vector>
#include <string>
using namespace std;

vector <string> words;

bool match(string path, string word){
    int pl = path.length(), wl = word.length(), j = 0;
    for(int i = 0; i < pl; i++){
        if(path[i] == word[j])
            j++;
    }
    if(j < wl)
        return false;
    return true;
}

int get_keyboard_row(char c){
    const char* args[] = {"qwertyuiop", "asdfghjkl", "zxcvbnm"};
    vector <string> keyboard(args, args + 3);
    
    for(int i = 0; i < keyboard.size(); i++){
        int n = keyboard[i].length();
        for(int j = 0; j < n; j++){
            if(keyboard[i][j] == c)
                return i;
        }
    }
}

vector <int> compress(vector <int> s){
    int i = 0, j = 0, n = s.size();
    while(i < n){
        if(s[i] != s[j])
            s[++j] = s[i];
        i++;
    }
    return vector <int>(s.begin(), s.begin() + j + 1);
}

int get_minimum_wordlength(string path){
    int n = path.length();
    vector <int> row_numbers(n);
    for(int i = 0; i < n; i++){
        row_numbers[i] = get_keyboard_row(path[i]);
    }

    int min_length = (compress(row_numbers)).size() - 3;
    if(min_length < 0)
        min_length = 0;
    return min_length;
}

vector<string> get_suggestions(string path){
    vector <string> suggestions_v1, suggestions_v2, suggestions_v3;
    int n = words.size(), pathlen = path.length();
    for(int i = 0; i < n; i++){
        int len = words[i].length();
        if(path[0] == words[i][0] && path[pathlen-1] == words[i][len-1]){
            suggestions_v1.push_back(words[i]);
        }
    }

    n = suggestions_v1.size();
    for(int i = 0; i < n ; i++){
        if(match(path, suggestions_v1[i])){
            suggestions_v2.push_back(suggestions_v1[i]);
        }
    }

    int min_length = get_minimum_wordlength(path);

    n = suggestions_v2.size();
    for(int i = 0; i < n; i++)
        if(suggestions_v2[i].length() > min_length)
            suggestions_v3.push_back(suggestions_v2[i]);

    return suggestions_v3;
}

void readfile(){
    words.clear();
    ifstream wordlist_file("wordlist.txt");
    string word;
    while(wordlist_file >> word)
        words.push_back(word);
    wordlist_file.close();
}

int main(){

    const char* args[] = {
        "heqerqllo",                             // hello
        "qwertyuihgfcvbnjk",                     // quick
        "wertyuioiuytrtghjklkjhgfd",             // world
        "dfghjioijhgvcftyuioiuytr",              // doctor
        "aserfcvghjiuytedcftyuytre",             // architecture
        "asdfgrtyuijhvcvghuiklkjuytyuytre",      // agriculture
        "mjuytfdsdftyuiuhgvc",                   // music
        "vghjioiuhgvcxsasdvbhuiklkjhgfdsaserty", // vocabulary 
    };
    vector<std::string> paths(args, args + 8);
    readfile();

    for(int i = 0; i < paths.size(); i++){
        vector <string> suggestions = get_suggestions(paths[i]);
        cout << "[";
        for(int j = 0; j < suggestions.size(); j++){
            cout << "'" << suggestions[j] << "'"; 
            if(j != suggestions.size() - 1)
                cout << ", ";
        }
        cout << "]" << endl;
    }
    return 0;
}

Thank you!
I assume MIT license too?

May I know why in line 75 "int min_length = (compress(row_numbers)).size() - 3;" the min_length should mhinus three? What does the number three mean??

In the example "aserfcvghjiuytedcftyuytre" -> "architecture", we change the keyboard rows 7 times, => a, e, f, c, g, i, c, t.
The idea is, the string to be searched will be at least 8 characters long since the user has left the keyboard row to reach a new key. We are relaxing the rule a bit (3 characters). It is purely a heuristic.

Ok, thanks for answering.