merge sort algorithm in CLR book explanation code example
Example 1: merge sort iterative (string)
//Joshua Khumalo
import java.util.Arrays;
public class Demo{
public static void merge_sort(int[] my_arr){
if(my_arr == null){
return;
}
if(my_arr.length > 1){
int mid = my_arr.length / 2;
int[] left = new int[mid];
for(int i = 0; i < mid; i++){
left[i] = my_arr[i];
}
int[] right = new int[my_arr.length - mid];
for(int i = mid; i < my_arr.length; i++){
right[i - mid] = my_arr[i];
}
merge_sort(left);
merge_sort(right);
int i = 0;
int j = 0;
int k = 0;
while(i < left.length && j < right.length){
if(left[i] < right[j]){
my_arr[k] = left[i];
i++;
} else {
my_arr[k] = right[j];
j++;
}
k++;
}
while(i < left.length){
my_arr[k] = left[i];
i++;
k++;
}
while(j < right.length){
my_arr[k] = right[j];
j++;
k++;
}
}
}
public static void main(String[] args){
int my_arr[] = {56, 78, 91, 21, 34, 0, 11};
int i=0;
merge_sort(my_arr);
System.out.println("The array after sorting is ");
for(i=0; i
Example 2: merge sort algorithm
/*
a[] is the array, p is starting index, that is 0,
and r is the last index of array.
*/
#include
// lets take a[5] = {32, 45, 67, 2, 7} as the array to be sorted.
// merge sort function
void mergeSort(int a[], int p, int r)
{
int q;
if(p < r)
{
q = (p + r) / 2;
mergeSort(a, p, q);
mergeSort(a, q+1, r);
merge(a, p, q, r);
}
}
// function to merge the subarrays
void merge(int a[], int p, int q, int r)
{
int b[5]; //same size of a[]
int i, j, k;
k = 0;
i = p;
j = q + 1;
while(i <= q && j <= r)
{
if(a[i] < a[j])
{
b[k++] = a[i++]; // same as b[k]=a[i]; k++; i++;
}
else
{
b[k++] = a[j++];
}
}
while(i <= q)
{
b[k++] = a[i++];
}
while(j <= r)
{
b[k++] = a[j++];
}
for(i=r; i >= p; i--)
{
a[i] = b[--k]; // copying back the sorted list to a[]
}
}
// function to print the array
void printArray(int a[], int size)
{
int i;
for (i=0; i < size; i++)
{
printf("%d ", a[i]);
}
printf("\n");
}
int main()
{
int arr[] = {32, 45, 67, 2, 7};
int len = sizeof(arr)/sizeof(arr[0]);
printf("Given array: \n");
printArray(arr, len);
// calling merge sort
mergeSort(arr, 0, len - 1);
printf("\nSorted array: \n");
printArray(arr, len);
return 0;
}