added merge sort in c (#39)

* add binary search in js

* added merge sort in c

sorting/README.md

@@ -5,8 +5,10 @@
 1. [Bubble Sort](c-or-cpp/bubble-sort.cpp)
 2. [Insertion Sort](c-or-cpp/insertion-sort.cpp)
 3. [Selection Sort](c-or-cpp/selection-sort.cpp)
+4. [Merge Sort](c-or-cpp/merge-sort.c)
 
 ### C#
+
 1. [Bubble Sort](csharp/bubble-sort.cs)
 2. [Insertion Sort](csharp/insertion-sort.cs)
 3. [Selection Sort](csharp/selection-sort.cs)

sorting/c-or-cpp/merge-sort.c

@@ -0,0 +1,89 @@
+#include <stdio.h>
+#include <stdlib.h>
+void merging(int a[], int l, int m, int r);
+void mergeSort(int a[], int l, int r);
+
+// Driver code
+int main()
+{
+    int n;
+    printf("Enter the size of the array:\n");
+    scanf("%d", &n);
+    int a[n];
+    printf("Enter the elements of the array:\n");
+    for (int i = 0; i < n; i++)
+        scanf("%d", &a[i]);
+    printf( "Given array is: ");
+    for (int i = 0; i < n; i++)
+        printf("%d ", a[i]);
+    mergeSort(a, 0, n - 1);
+    printf( "\nSorted array is: ");
+    for (int i = 0; i < n; i++)
+        printf("%d ", a[i]);
+    return 0;
+}
+
+// Merges two subarrays of a[].
+// First subarray is a[l..m]
+// Second subarray is a[m+1..r]
+void merging(int a[], int l, int m, int r)
+{
+    int n1 = m - l + 1;
+    int n2 = r - m;
+    int Left[n1], Right[n2];        // Creating temporary arrays
+
+    // Copy data to temp arrays Left[] and Right[]
+    for (int i = 0; i < n1; i++)
+        Left[i] = a[l + i];
+    for (int j = 0; j < n2; j++)
+        Right[j] = a[m + 1 + j];
+
+    int p = 0, q = 0, k = l;
+    while (p < n1 && q < n2)
+    {
+        if (Left[p] <= Right[q])
+        {
+            a[k] = Left[p];
+            p++;
+        }
+        else
+        {
+            a[k] = Right[q];
+            q++;
+        }
+        k++;
+    }
+
+    // Copy the remaining elements of
+	// Left[], if there are any
+    while (p < n1)
+    {
+        a[k] = Left[p];
+        p++;
+        k++;
+    }
+
+    // Copy the remaining elements of
+	// Right[], if there are any
+    while (q < n2)
+    {
+        a[k] = Right[q];
+        q++;
+        k++;
+    }
+}
+
+
+// l is for left index and r is
+// right index of the sub-array
+// of arr to be sorted 
+void mergeSort(int a[], int l, int r)
+{
+    if (l < r)
+    {
+        int m = l + (r - l) / 2;
+        mergeSort(a, l, m);
+        mergeSort(a, m + 1, r);
+        merging(a, l, m, r);
+    }
+}