added mergesort algorithm implemented in c

Author: caffeine-soul

merge.cpp

@@ -0,0 +1,102 @@
+#include<stdlib.h> 
+#include<stdio.h> 
+  
+// Merges two subarrays of arr[]. 
+// First subarray is arr[l..m] 
+// Second subarray is arr[m+1..r] 
+void merge(int arr[], int l, int m, int r) 
+{ 
+    int i, j, k; 
+    int n1 = m - l + 1; 
+    int n2 =  r - m; 
+  
+    /* create temp arrays */
+    int L[n1], R[n2]; 
+  
+    /* Copy data to temp arrays L[] and R[] */
+    for (i = 0; i < n1; i++) 
+        L[i] = arr[l + i]; 
+    for (j = 0; j < n2; j++) 
+        R[j] = arr[m + 1+ j]; 
+  
+    /* Merge the temp arrays back into arr[l..r]*/
+    i = 0; // Initial index of first subarray 
+    j = 0; // Initial index of second subarray 
+    k = l; // Initial index of merged subarray 
+    while (i < n1 && j < n2) 
+    { 
+        if (L[i] <= R[j]) 
+        { 
+            arr[k] = L[i]; 
+            i++; 
+        } 
+        else
+        { 
+            arr[k] = R[j]; 
+            j++; 
+        } 
+        k++; 
+    } 
+  
+    /* Copy the remaining elements of L[], if there 
+       are any */
+    while (i < n1) 
+    { 
+        arr[k] = L[i]; 
+        i++; 
+        k++; 
+    } 
+  
+    /* Copy the remaining elements of R[], if there 
+       are any */
+    while (j < n2) 
+    { 
+        arr[k] = R[j]; 
+        j++; 
+        k++; 
+    } 
+} 
+  
+/* l is for left index and r is right index of the 
+   sub-array of arr to be sorted */
+void mergeSort(int arr[], int l, int r) 
+{ 
+    if (l < r) 
+    { 
+        // Same as (l+r)/2, but avoids overflow for 
+        // large l and h 
+        int m = l+(r-l)/2; 
+  
+        // Sort first and second halves 
+        mergeSort(arr, l, m); 
+        mergeSort(arr, m+1, r); 
+  
+        merge(arr, l, m, r); 
+    } 
+} 
+  
+/* UTILITY FUNCTIONS */
+/* Function to print an array */
+void printArray(int A[], int size) 
+{ 
+    int i; 
+    for (i=0; i < size; i++) 
+        cout<<A[i]; 
+    cout<<"\n"; 
+} 
+  
+/* Driver program to test above functions */
+int main() 
+{ 
+    int arr[] = {12, 11, 13, 5, 6, 7}; 
+    int arr_size = sizeof(arr)/sizeof(arr[0]); 
+  
+    cout<< "Given array is \n"; 
+    printArray(arr, arr_size); 
+  
+    mergeSort(arr, 0, arr_size - 1); 
+  
+    cout<<"\nSorted array is \n"; 
+    printArray(arr, arr_size); 
+    return 0; 
+}