Merge pull request larissalages#263 from mulirow/add-comb-sort

Added combsort.cpp

Author: larissalages

classical_algorithms/c++/combsort.cpp

@@ -0,0 +1,53 @@
+#include<bits/stdc++.h> 
+using namespace std; 
+  
+//Comb sort is an improvement over bubble sort, and works by varying the gap when comparing values. It has better average time, but worst case scenario is still the same.
+
+//Algorithm:
+int nextGap(int gap){
+    //Curiosity: this shrink factor for the gap (~=1.3) has been suggested as the ideal one by the original authors of this sorting algorithm, but can actually be changed.
+    gap = (gap*10)/13; 
+  
+    if(gap < 1){
+        return 1; 
+    }
+    return gap; 
+} 
+  
+void combSort(int array[], int n){ 
+    int gap = n; 
+    //The purpose of the flag is the same as in bubble sort.
+    bool flag = true; 
+   
+    while (gap != 1 || flag == true){ 
+        gap = nextGap(gap); 
+        flag = false; 
+  
+        for (int i = 0; i < (n - gap); i++){ 
+            if(array[i] > array[i + gap]){ 
+                swap(array[i], array[i + gap]); 
+                flag = true; 
+            } 
+        } 
+    } 
+} 
+
+//Test:
+int main(){
+    int n;
+    int array[] = {3, 1, 2, 9, -21, 14, 15, 12, 13, 12};
+    n = sizeof(array) / sizeof(array[0]);
+    cout << "Elements before comb sort:\n";
+    for (int i = 0; i < n; i++){
+        cout << array[i] << " ";
+    }
+    cout << "\n";
+
+    combSort(array, n);
+    
+    cout << "Elements after comb sort:\n";
+    for(int i = 0; i < n; i++){
+        cout << array[i] << " ";
+    }
+    cout << "\n";
+}

readme.md

@@ -48,6 +48,7 @@ Code | Test
 [Insertion Sort](https://github.com/larissalages/code_problems/blob/master/classical_algorithms/c++/insertionsort.cpp) | Missing tests
 [Bubble Sort](https://github.com/larissalages/code_problems/blob/master/classical_algorithms/c++/bubblesort.cpp) | Missing tests
 [Merge Sort](https://github.com/larissalages/code_problems/blob/master/classical_algorithms/c%2B%2B/mergesort.cpp) | Missing tests
+[Comb Sort](https://github.com/larissalages/code_problems/blob/master/classical_algorithms/c%2B%2B/combsort.cpp) | Missing Tests
 [Quick Sort](https://github.com/larissalages/code_problems/blob/master/classical_algorithms/c++/quicksort.cpp) | Missing tests
 [0/1 Knapsack Problem](https://github.com/larissalages/code_problems/blob/master/classical_algorithms/c%2B%2B/01_knapsack_problem.cpp) | Missing tests
 [Kadane's Algorithm](https://github.com/larissalages/code_problems/blob/master/classical_algorithms/c%2B%2B/Kadane_Algorithm.cpp) | Missing tests