Create Perfect Keyboard.cpp

Author: MathProgrammer

2020/Educational Rounds/Educational Round 82/Programs/Perfect Keyboard.cpp

@@ -0,0 +1,158 @@
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+const int NO_OF_ALPHABETS = 26;
+vector <int> degree(NO_OF_ALPHABETS, 0);
+vector <int> graph[NO_OF_ALPHABETS];
+vector <int> component_no(NO_OF_ALPHABETS, 0);
+
+void dfs(int v, int parent_v, int c)
+{
+    //cout << "V = " << v << " C = " << c << "\n";
+    component_no[v] = c;
+    
+    for(int i = 0; i < graph[v].size(); i++)
+    {
+        int child_v = graph[v][i];
+        
+        if(child_v == parent_v || component_no[child_v] == c)
+        {
+            continue;
+        }
+        
+        dfs(child_v, v, c);
+    }
+}
+
+void solve()
+{
+    string password;
+    cin >> password;
+    
+    const int NO_OF_ALPHABETS = 26;
+    vector <vector <int> > adjacency(NO_OF_ALPHABETS,
+                                     vector <int> (NO_OF_ALPHABETS, false));
+    
+    for(int alpha = 0; alpha < NO_OF_ALPHABETS; alpha++)
+    {
+        degree[alpha] = 0;
+        
+        graph[alpha].clear();
+        
+        component_no[alpha] = 0;
+    }
+    
+    for(int i = 1; i < password.size(); i++)
+    {
+        if(adjacency[password[i] - 'a'][password[i - 1] - 'a'] == false)
+        {
+            adjacency[password[i] - 'a'][password[i - 1] - 'a'] = true;
+            adjacency[password[i - 1] - 'a'][password[i] - 'a'] = true;
+                                         
+            graph[password[i] - 'a'].push_back(password[i - 1] - 'a');
+            graph[password[i - 1] - 'a'].push_back(password[i] - 'a');
+            
+            degree[password[i] - 'a']++;
+            degree[password[i - 1] - 'a']++;
+        }
+        
+    }
+    
+    for(int alpha = 0; alpha < NO_OF_ALPHABETS; alpha++)
+    {
+        if(degree[alpha] > 2)
+        {   
+            cout << "NO\n";
+            return;
+        }
+    }
+    
+    int component = 1;
+    
+    for(int alpha = 0; alpha < NO_OF_ALPHABETS; alpha++)
+    {
+        if(component_no[alpha] == 0)
+        {
+            dfs(alpha, -1, component++);
+        }
+    }
+    
+    string keyboard;
+    vector <int> components;
+    vector <int> used(NO_OF_ALPHABETS, false);
+    for(int c = 1; c < component; c++)
+    {
+        vector <int> this_component;
+        for(int alpha = 0; alpha < NO_OF_ALPHABETS; alpha++)
+        {
+            if(component_no[alpha] == c)
+            {
+                this_component.push_back(alpha);
+            }
+        }
+        
+        if(this_component.size() == 1)
+        {
+            keyboard += (char)('a' + this_component[0]);
+            used[this_component[0]] = true;
+            continue;
+        }
+        
+        int border_1 = -1, border_2 = -1;
+        for(int i = 0; i < this_component.size(); i++)
+        {
+            if(degree[this_component[i]] == 1)
+            {
+                if(border_1 == -1)
+                    border_1 = this_component[i];
+                else
+                    border_2 = this_component[i];
+            }
+        }
+        
+        if(border_1 == -1 || border_2 == -1)
+        {
+            cout << "NO\n";
+            
+            return;
+        }
+        
+        keyboard += (char)('a' + border_1);
+        used[border_1] = true;
+        
+        while(keyboard.back() - 'a' != border_2)
+        {
+            for(int i = 0; i < graph[keyboard.back() - 'a'].size(); i++)
+            {
+                if(!used[graph[keyboard.back() - 'a'][i]])
+                {
+                    int next = graph[keyboard.back() - 'a'][i];
+                    
+                    keyboard += (char)('a' + next);
+                    
+                    used[next] = true;
+                    
+                    break;
+                }
+            }
+        }
+        
+    }
+   
+    cout << "YES\n";
+    cout << keyboard << "\n";
+    return;
+}
+
+int main()
+{
+    int no_of_test_cases;
+    cin >> no_of_test_cases;
+    
+    while(no_of_test_cases--)
+        solve();
+    
+    return 0;
+}