Merge Sort Visualisation

Merge Sort Visualisation in C

In this program 100 random numbers are generated which are represented on x-y graph using lines

and merge sort is applied on the array, as elements changes their position the graph is redrawn and the visualisation can be seen. Also current position of index is shown by red lines.

Below is the code written in C language.

Compiler used - GCC

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#include<stdio.h>

#include<graphics.h>

#include<time.h> 

int maxy=480;

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++;

delay(8);

cleardevice();

for(int z=0;z<100;z++)

{

if(z==i || z==j || z==k)

setcolor(RED);

line((4*z)+120,maxy-arr[z],(4*z)+120,maxy);

if(z==i || z==j  || z==k)

setcolor(WHITE);

} 

    } 

  

    /* Copy the remaining elements of L[], if there 

       are any */

    while (i < n1) 

    { 

        arr[k] = L[i]; 

        i++; 

        k++; 

delay(8);

cleardevice();

for(int z=0;z<100;z++)

{

if(z==i || z==j  || z==k)

setcolor(RED);

line((4*z)+120,maxy-arr[z],(4*z)+120,maxy);

if(z==i || z==j  || z==k)

setcolor(WHITE);

} 

    } 

  

    /* Copy the remaining elements of R[], if there 

       are any */

    while (j < n2) 

    { 

        arr[k] = R[j]; 

        j++; 

        k++; 

delay(8);

cleardevice();

for(int z=0;z<100;z++)

{

if(z==i || z==j  || z==k)

setcolor(RED);

line((4*z)+120,maxy-arr[z],(4*z)+120,maxy);

if(z==i || z==j  || z==k)

setcolor(WHITE);

} 

    } 

} 

  

/* 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); 

    } 

} 

int main()

{

int gd=DETECT,gm;

srand(time(0)); 

int temp,n,i,k,j,arr[100];

for(i=0;i<100;i++)

arr[i] = rand()%480;

initgraph(&gd,&gm,NULL);

mergeSort(arr, 0, 99);

scanf("%d",&n);

closegraph();

}

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