merge sort using java code example
Example 1: merge sort java
public static void mergeSort(int[] a, int n) {
if (n < 2) {
return;
}
int mid = n / 2;
int[] l = new int[mid];
int[] r = new int[n - mid];
for (int i = 0; i < mid; i++) {
l[i] = a[i];
}
for (int i = mid; i < n; i++) {
r[i - mid] = a[i];
}
mergeSort(l, mid);
mergeSort(r, n - mid);
merge(a, l, r, mid, n - mid);
}
public static void merge(
int[] a, int[] l, int[] r, int left, int right) {
int i = 0, j = 0, k = 0;
while (i < left && j < right) {
if (l[i] <= r[j]) {
a[k++] = l[i++];
}
else {
a[k++] = r[j++];
}
}
while (i < left) {
a[k++] = l[i++];
}
while (j < right) {
a[k++] = r[j++];
}
}
Example 2: mergesort java
public class MergeSort
{
public static void main(String[] args)
{
int i;
int values[] = new int[11];
for(i=0; i<values.length; i++) { values[i]=values.length-i; }
print(values);
sort(values,0,values.length-1);
print(values);
}
public static void sort(int[] numbers, int p,int r)
{
int q;
if(p<r)
{
q = (p+r)/2;
sort(numbers,p,q);
sort(numbers,q+1,r);
merge(numbers,p,q,r);
}
}
private static void merge(int[] values, int p, int mid, int r)
{
int i,j,k;
int n1 = mid - p + 1;
int n2 = r - mid;
int[] left = new int[n1+1];
int[] right = new int[n2+1];
for(i=0; i<n1; i++)
{
left[i] = values[ p + i ];
}
for(j=0; j<n2; j++)
{
right[j] = values[mid + j + 1];
}
left[n1] = Integer.MAX_VALUE;
right[n2] = Integer.MAX_VALUE;
i=0; j=0;
for(k=p; k<=r; k++)
{
if(left[i]<=right[j])
{
values[k] = left[i];
i = i + 1;
}
else
{
values[k] = right[j];
j = j + 1;
}
}
}
public static void print(int[] numbers)
{
int i;
for(i=0; i<numbers.length; i++)
{
System.out.print(numbers[i]+ " ");
}
System.out.println();
}
}