Merge pull request #78 from neha030/devp5

merge sort added

merge.cpp

@@ -0,0 +1,79 @@
+#include<bits/stdc++.h>
+using namespace std;
+void merge(int a[],int l,int mid,int r)
+{
+    int n1=mid-l+1;
+    int n2=r-mid;
+    int b[n1];
+    int c[n2];
+    for(int i=0;i<n1;i++)
+    {
+    b[i]=a[l+i];
+    }
+    for(int i=0;i<n2;i++)
+    {
+    c[i]=a[mid+1+i];
+    }
+    int i=0;
+    int j=0;
+    int k=l;
+    while(i<n1 &&j<n2)
+    {
+        if(b[i]<c[j])
+        {
+        a[k]=b[i];
+        k++;
+        i++;
+        }
+        else
+        {
+            a[k]=c[j];
+            k++;
+            j++;
+
+
+
+        }
+
+
+
+    }
+    while(i<n1)
+    {
+      a[k]=b[i];
+        k++;
+        i++;  
+    }
+    while(j<n2)
+    {
+            a[k]=c[j];
+            k++;
+            j++;   
+    }
+
+}
+void mergesort(int a[],int l,int r)
+{
+    if(l<r)
+    {
+    int mid =(l+r)/2;
+    mergesort(a,l,mid);
+    mergesort(a,mid+1,r);
+
+    merge(a,l,mid,r);
+    }
+
+
+}
+int main()
+{
+    int a[]={5,4,3,2,1};
+    mergesort(a,0,4);
+    for(int i=0;i<5;i++)
+    {
+        cout<<a[i]<<"  ";
+    }
+    cout<<endl;
+    return 0;
+
+}