C program to implement MERGE sort.

Posted on October 13, 2011 by Sandeepa Nadahalli

Merge sort is based on the divide conquer strategy. Array is divided in to two halves.if the array length is n, then it is divided into n/2,n/4,n/8…. and each part is sorted independently, then conquered into the sorted array. The efficiency of merge sort is O(n log n). Read more about C Programming Language .

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#include <stdio.h>
#include <stdlib.h>

#define MAX_ARY 10

void merge_sort(int x[], int end, int start);

int main(void) {
 int ary[MAX_ARY];
 int j = 0;

 printf("nnEnter the elements to be sorted: n");
 for(j=0;j<MAX_ARY;j++)
  scanf("%d",&ary[j]);

 /* array before mergesort */
 printf("Before    :");
 for(j = 0; j < MAX_ARY; j++)
  printf(" %d", ary[j]);

 printf("n");

 merge_sort(ary, 0, MAX_ARY - 1);

 /* array after mergesort */
 printf("After Merge Sort :");
 for(j = 0; j < MAX_ARY; j++)
  printf(" %d", ary[j]);

 printf("n");
 getch();
}

/* Method to implement Merge Sort*/
void merge_sort(int x[], int end, int start) {
 int j = 0;
 const int size = start - end + 1;
 int mid  = 0;
 int mrg1 = 0;
 int mrg2 = 0;
 int executing[MAX_ARY];

 if(end == start)
  return;

 mid  = (end + start) / 2;

 merge_sort(x, end, mid);
 merge_sort(x, mid + 1, start);

 for(j = 0; j < size; j++)
  executing[j] = x[end + j];

 mrg1 = 0;
 mrg2 = mid - end + 1;

 for(j = 0; j < size; j++) {
  if(mrg2 <= start - end)
   if(mrg1 <= mid - end)
    if(executing[mrg1] > executing[mrg2])
     x[j + end] = executing[mrg2++];
    else
     x[j + end] = executing[mrg1++];
   else
    x[j + end] = executing[mrg2++];
  else
   x[j + end] = executing[mrg1++];
 }
}

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C Program to generate random numbers.

Posted on October 12, 2011 by Sandeepa Nadahalli

C Program to generate random numbers. Random Numbers are numbers which are produced by a process and its outcome is unpredictable.The function srand() is used to seed the random sequence. The rand() function shall compute a sequence of pseudo-random integers in the range [0, {RAND_MAX}] with a period of at least 2^32.
Read more about C Programming Language .

/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

main() {
 int i, num;
 printf("Enter how many random numbers you want?n");
 scanf("%d", &num);
 //The function srand() is used to seed the random sequence. 
 //srand() will generate a specific "random" sequence over and over again. 
 srand(time(NULL));
 //The rand() function shall compute a sequence of pseudo-random 
 //integers in the range [0, {RAND_MAX}]  with a period of at least 2^32.
 for (i = 0; i < num; i++) {
  printf("random_number[%d]= %dn", i + 1, rand());
 }

 printf("A number between 0 and 99: %dn", rand() % 100);

 printf("A number between 0 and 9: %dn", rand() % 10);

 return 0;
}

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