quick.cpp added

Author: amal-san

data structures/quick.cpp

@@ -0,0 +1,76 @@
+#include <stdio.h>
+#include <stdlib.h>
+ 
+void swap(int *x,int *y);
+int choose_pivot(int i,int j );
+void quicksort(int list[],int m,int n);
+void display(int list[],const int n);
+ 
+void main()
+{
+    const int SIZE = 10;
+    int list[SIZE];
+ 
+    int i = 0;
+ 
+    /* generates random numbers and fill the list */
+    for(i = 0; i < SIZE; i++ )
+        list[i] = rand();
+ 
+    printf("The list before sorting is:\n");
+    display(list,SIZE);
+ 
+    /* sort the list using quicksort algorithm */
+    quicksort(list,0,SIZE-1);
+ 
+    printf("The list after sorting:\n");
+    display(list,SIZE);
+}
+ 
+void swap(int *x,int *y)
+{
+    int temp;
+    temp = *x;
+    *x = *y;
+    *y = temp;
+}
+ 
+int choose_pivot(int i,int j )
+{
+    return((i+j) /2);
+}
+ 
+void quicksort(int list[],int m,int n)
+{
+    int key,i,j,k;
+    if( m < n)
+    {
+        k = choose_pivot(m,n);
+        swap(&list[m],&list[k]);
+        key = list[m];
+        i = m+1;
+        j = n;
+        while(i <= j)
+        {
+            while((i <= n) && (list[i] <= key))
+                i++;
+            while((j >= m) && (list[j] > key))
+                j--;
+            if( i < j)
+                swap(&list[i],&list[j]);
+        }
+        /* swap two elements */
+        swap(&list[m],&list[j]);
+ 
+        /* recursively sort the lesser list */
+        quicksort(list,m,j-1);
+        quicksort(list,j+1,n);
+    }
+}
+void display(int list[],const int n)
+{
+    int i;
+    for(i=0; i<n; i++)
+        printf("%d\t",list[i]);
+}
+