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MergeSort.java
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196 lines (174 loc) · 5.82 KB
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package sorting_searching;
import java.util.Comparator;
public class MergeSort {
public static void main(String[] args) {
int[] array = {91, 34, 86, 39, 27, 87, 70, 48, 100, 95};
// Example:
int[] array1 = array.clone();
mergeSort(array1);
System.out.println(java.util.Arrays.toString(array1)); // [27, 34, 39, 48, 70, 86, 87, 91, 95, 100]
int[] array2 = array.clone();
straightMergeSort(array2);
System.out.println(java.util.Arrays.toString(array2)); // [27, 34, 39, 48, 70, 86, 87, 91, 95, 100]
int[] array3 = array.clone();
naturalMergeSort(array3);
System.out.println(java.util.Arrays.toString(array3)); // [27, 34, 39, 48, 70, 86, 87, 91, 95, 100]
}
public static void mergeSort(int[] a) {
mergeSort(a, 0, a.length - 1);
}
private static void mergeSort(int[] a, int left, int right) {
if (left < right) {
int middle = (left + right) / 2;
mergeSort(a, left, middle);
mergeSort(a, middle + 1, right);
merge(a, left, middle, right);
}
}
public static <T extends Comparable<? super T>> void mergeSort(T[] a) {
mergeSort(a, Comparator.naturalOrder());
}
public static <T> void mergeSort(T[] a, Comparator<T> comp) {
mergeSort(a, comp, 0, a.length - 1);
}
private static <T> void mergeSort(T[] a, Comparator<T> comp, int left, int right) {
if (left < right) {
int middle = (left + right) / 2;
mergeSort(a, comp, left, middle);
mergeSort(a, comp, middle + 1, right);
merge(a, comp, left, middle, right);
}
}
public static void straightMergeSort(int[] a) {
for (int length = 1; length < a.length; length *= 2) {
int right = -1;
while (right + length < a.length) {
int left = right + 1;
int middle = left + length - 1;
right = Math.min(middle + length, a.length - 1);
merge(a, left, middle, right);
}
}
}
public static <T extends Comparable<? super T>> void straightMergeSort(T[] a) {
straightMergeSort(a, Comparator.naturalOrder());
}
public static <T> void straightMergeSort(T[] a, Comparator<T> comp) {
for (int length = 1; length < a.length; length *= 2) {
int right = -1;
while (right + length < a.length) {
int left = right + 1;
int middle = left + length - 1;
right = Math.min(middle + length, a.length - 1);
merge(a, comp, left, middle, right);
}
}
}
public static void naturalMergeSort(int[] a) {
int left;
do {
int right = -1;
left = 0;
while (right < a.length - 1) {
left = right + 1;
int middle = left;
while (middle < a.length - 1 && a[middle + 1] >= a[middle]) {
++middle;
}
if (middle < a.length - 1) {
right = middle + 1;
while (right < a.length - 1 && a[right + 1] >= a[right]) {
++right;
}
merge(a, left, middle, right);
} else {
right = a.length - 1;
}
}
} while (left > 0);
}
public static <T extends Comparable<? super T>> void naturalMergeSort(T[] a) {
naturalMergeSort(a, Comparator.naturalOrder());
}
public static <T> void naturalMergeSort(T[] a, Comparator<T> comp) {
int left;
do {
int right = -1;
left = 0;
while (right < a.length - 1) {
left = right + 1;
int middle = left;
while (middle < a.length - 1 && comp.compare(a[middle + 1], a[middle]) >= 0) {
++middle;
}
if (middle < a.length - 1) {
right = middle + 1;
while (right < a.length - 1 && comp.compare(a[right + 1], a[right]) >= 0) {
++right;
}
merge(a, comp, left, middle, right);
} else {
right = a.length - 1;
}
}
} while (left > 0);
}
private static void merge(int[] a, int left, int middle, int right) {
int[] b = new int[right - left + 1];
int i = left;
int j = middle + 1;
int k = 0;
while (i <= middle && j <= right) {
if (a[i] <= a[j]) {
b[k] = a[i];
++i;
} else {
b[k] = a[j];
++j;
}
++k;
}
while (i <= middle) {
b[k] = a[i];
++i;
++k;
}
while (j <= right) {
b[k] = a[j];
++j;
++k;
}
for (k = left; k <= right; ++k) {
a[k] = b[k - left];
}
}
private static <T> void merge(T[] a, Comparator<T> comp, int left, int middle, int right) {
Object[] b = new Object[right - left + 1];
int i = left;
int j = middle + 1;
int k = 0;
while (i <= middle && j <= right) {
if (comp.compare(a[i], a[j]) <= 0) {
b[k] = a[i];
++i;
} else {
b[k] = a[j];
++j;
}
++k;
}
while (i <= middle) {
b[k] = a[i];
++i;
++k;
}
while (j <= right) {
b[k] = a[j];
++j;
++k;
}
for (k = left; k <= right; ++k) {
a[k] = (T) b[k - left];
}
}
}